* Rewrite/refactor "Uninstall" menu item function

NOTE: This function wasn't tested yet. This commit is a backup commit.

* Rewrite/refactor "Update All" menu item function (1/X)

* Rewrite/refactor "Uninstall" menu item function

NOTE: There is a problem during refiltering after uninstalling when
      "Show Installed Apps" button is toggled.

* Re-implement installing from file with command-line argument

* Refactor flatpakguiapp.py

* Remove "Install From Entry" and "Install From File" menu item functions.
  They are useless when a search bar is available.

* Rename some UI objects
* Fix Turkish

* Rewrite "Install From Entry" menu item function

* Rewrite installwindow.py (3/3)

* Rewrite installwindow.py (2/X)

* Rewrite installwindow.py (1/X)
* Add a FIXME to mainwindow.py
* Fix (?) a warning when main window is closed

* Refactor mainwindow.py and infowindow.py (2/X)
* Fix "Info" menu item function

* Rename/refactor mainwindow.py methods (3/X)

* Rename/refactor mainwindow.py methods (2/X)

* Rename/refactor mainwindow.py methods

* Rewrite mainwindow.py __init__ function (2/2)

* Rewrite mainwindow.py __init__ function (1/X)

* Remove unnecessary whitespace
* Add a FIXME for running when argument count is two

- Fix "Install From Entry" menu item function
- Simplify some code

- Fix "Uninstall" menu item function
- Simplify some "Install" menu item function code

* Divide menu to two separate menu
* Fix actions (1/X)