Improved History (With Shortcut) av Windows_2000

I modified manifest.json to include a shortcut.
Original extension by [Karl](https://addons.mozilla.org/en-US/firefox/user/13834224/)
----------------------
Improved History is an addon that let you render your browser history in toolbar popup UI in a stylish manner.

This addon can basically be a substitute for history page in your browser. Once you open toolbar popup you will see the activity tab (first tab on top left corner). Within the activity tab there are weekdays listed horizontally. Below that there are the history items listed vertically.

Simply click on a day and the vertical list will jump to the specified day. Each history item has a - delete - button next to it. Moreover, you can click on the - more from site - button to see all items related to this one within the history.

There is also a search tab next to the activity tab which you can use to search for desired keywords within the history. The last tab is for the addon settings. Currently, it has a single button to clear all history. Please note that, clearing history with this addon is irreversible. In other words, you cannot bring back the deleted items in the history once they are cleared.