X11: Set correct WM_CLASS property to windows

Closes #968
Don't leak when setting WM_CLASS
Define QzTools::setWmClass on all platforms.

Get rid of #ifdef's and make it do nothing on non X11.
Fix compile on non X11 platforms
What is this? I didn't write it ...
Set WM_CLASS also to Download Manager.
[ThemeManager] Fixed crash on saving settings when theme is unavailable.
Fixed compilation with Qt 5
GreaseMonkey: Run usercscripts in all frames on page

Conflicts:
	CHANGELOG
	src/plugins/GreaseMonkey/gm_manager.cpp
	src/plugins/GreaseMonkey/gm_plugin.cpp
Fixed Accept-Language header so it works with all sites
Removed link for removing cookies from Adobe Flash Player
SpeedDial: Replaced facebook with duckduckgo as default page

Closes #990
Set DuckDuckGo as a default search engine
Fix using external download manager with use defined location setting.

Closes #984
Make SchemeHandler destructor virtual
License Viewer: Use Courier font + small visual tweaks

Added close button and changed default size
Fixed building and updated changelog