[AdBlockDialog] Options button is now QPushButton

Qt renders better down icon indicating the button has menu
[Buttons] Use QPushButton for buttons with menu everywhere
[ComboTabBar] Fixed isOverflowed() for empty tabbar.

It returned true for empty tabbar. Switching tabs with
mouse wheel now works correctly in all scenarios.
[CommandLineOptions] Change Qt url to qt-project.com
[CommandLineOptions] New option to toggle fullscreen.
[Portable] Portable mode can now be enabled with commandline option

It is not needed to rebuild for Portable mode.
However, it is still possible to enforce portable mode with
PORTABLE_BUILD build option.

Conflicts:
	src/lib/app/mainapplication.cpp
[scripts] translations_update now generates transifex friendly ts file

See #1143
[code] Coding style
[SBI_JsIcon] Fix after 36724df3a69

Closes #1174
[AdBlockDialog] Change AdBlockDialog to QWidget

Closes #1169
[AdBlockTreeWidget] Greatly speedup loading rules from subscriptions

Don't use per-pixel scrolling. For some reason, it massively slows
rendering of TreeWidget

See #1169
[DownloadManager] Change "Remove" -> "Remove From List"

Closes #1162
[WindowsJumpList] Add new entry "Open new private window"

Closes #1155