Swedish translation

- Arabic translation by Essam Ambr aka (JaMaYcKa)
- Minor compatibility improvements

In expert mode allow for the replacement text also $&$URL, $URL$&, $&$NAME, $NAME$&, $&$TITLE, and $TITLE$&.

Fix strip bookmarks and moving to "Dupes" folder: Regression from 6.1
Slight clarification in English/German/Spanish formulation for count messages

- Update uk, ru locales (Henaro aka Ironwool)
- Slight clarification in English formulation for non-dupe bookmarks
- Minor internal changes (compatibility with chrome)

Add non-dupes button

Update of translations: de, es

Update UK translation
Fixed minimally supported version

Update locales: uk ru

Fix regression from 5.6 which caused a complete failure:
https://github.com/vaeth/bookmarkdupes/issues/66

Major layout change:

• Use textarea instead of input field

Minor changes:

• Minor layout changes: Warning placement, table head, arrows
• Explicitly test for availability of the bookmark API
• Fixed minor mistakes in DOM tree which worked only by accident
• Internal: use generic wrapper functions for DOM appending
• Internal: use clean HTML5 which passes https://validator.w3.org/
• Internal: remove redundant checks
• Internal: avoid unnecessary function nesting

Minor compatibility improvements

Optical changes:

• Redesign of icon
• Add favicon
• Page heading with icon and name of the extension
• Add warnings about expert mode and for removal/strip button

FIx regression from 5.1:
radio buttons in expert mode now enable/disable correct columns again.
Thanks to perdolka for reporting: https://github.com/vaeth/bookmarkdupes/issues/56

Main Change:

”Expert options“ have been added: It is now possible to define rules
in order to

1. ignore certain bookmarks, i.e. to not consider them as duplicate, and
2. to define when two bookmarks are to be considered as duplicate.

The rules are defined in terms of regular expressions (of javascript flavor);
that's why some expert knowledge is needed to use them.
It is possible to store the rules in local storage or in sync storage;
therefore, storage permissions are required now.
(It is not possible to require permissions for storage only when needed.)

Other Changes:

• The button for ”Similar Dupes“ has been removed:
  This can now be defined by the expert options, instead.
  Be aware that the default expert options differ from the previous meaning
  of ”similar dupes“: The \? tails rule is now by default deactivated, because
  it has too many false positives. Instead, some relatively safe rules are
  active in the defaults, and in addition one locale-specific example of a
  filter rule.
• The ”tabs“ permission is no longer required.
  The disadvantage of this relaxation is that it is now possible to open several
  copies of the extension in different tabs which might be confusing.
• bugfix: increase minimal required gecko version to 48.0, see
  https://github.com/vaeth/bookmarkdupes/issues/44
• bugfix: calculation error messages are now displayed correctly
• bugfix: use safe ids for bookmarks; previously (theoretically) some
  clashes could occur with ids on the page, possibly leading to strange
  behaviour
• bugfix: Some forgotten semicolons have been added in the code.
  This might have been a reason for
  https://github.com/vaeth/bookmarkdupes/issues/38
  (Although the options page was meant as a workaround for that bug, it has
  currently not been removed, since it might be convenient for some users.)
• Internal code improvements: Removing of redundant codd (SplitNumber),
  avoid javascript trickery, use clearer function names

Updated Languages:

• uk, ru (by Henaro aka Ironwool)
• es (by Juan Salvador Aleixandre Talens)
• de (by Martin Väth)

Main change:

Now a tab is used instead of a panel: This should speed up a lot!
Internally, this meant a major rewrite (eliminating the former background process completely).

Other major changes:

• Bookmarks are displayed as clickable links which open in a new tab
• Now folders can be selected for marking actions (instead of only the 2 top level folders)
• There are new buttons for not marking the first/last/oldest/newest for folder
• Optically, the buttons for marking folders appear only if a folder is selected. Thanks to perdolka for the idea: https://github.com/vaeth/bookmarkdupes/issues/32

Minor changes, cosmetics, bugfixes:

• The description of the list appears now as titles if the mouse hovers over the texts above the list
• Add a checkbox to disable counting
• Updating of translations for es, uk, ur; some spelling/grammar fixes for en
• Disable checkboxes while updating them
• bugfix: try to force display (disable) syncing with setTimeout()
• bugfix: mark also last group for folder/category selection
• internal: prefer const over let if possible
• internal: avoid new Array()