[Build] Correctly choose /usr/lib/i386-linux-gnu as LIBDIR on 32b Debian

QMAKE_HOST.arch is empty on x86
Fix compile error with vc++ 2013

Qz::VERSION is not exported
[ToolButton] Use QImage for multiIcon

Instead of 4 separate QPixmaps, use just one QImage and paint only
the current part (according to button state) of the image on button.
[Bookmarks] Use keyword as a shortcut for bookmark url in LocationBar

It is now possible to load bookmarks only with entering its keyword in
LocationBar and then pressing Enter (no need to select the bookmark
from popup completion).
[DataPaths] USE_LIBPATH is always defined on Unix

No need to add "/usr/lib/qupzilla" to the Plugins path if
USE_LIBPATH is not set, as "/usr/lib/qupzilla" won't exist on
non-Unix platform.

[ci skip]
[Mac] Use ~/Library/Application Support/QupZilla as ConfigPath

+ little cleanup in variable naming (homePath -> oldConfPath)

See #1302
[DataPaths] Use classic array instead of QHash for storing paths
[Transifex] Added .tx/config

Translations can now be pulled with "tx pull -a"
[Translations] Pulled translations from Transifex
[GreaseMonkey] Fixed downloading scripts to correct directory
[Translations] Removed sr@Ijekavian translations (with capital I)

[ci skip]
Merge pull request #1305 from char101/bug/fix-compile-error-1

Fix compile error with vc++ 2013
Ignore netbeans
Merge branch 'master' of https://github.com/QupZilla/qupzilla.git
[QtWebEngine] Update port on top of current master
Updated README.md
[QtWebEngine] Call QWebEngine::initialize to fix HTML5 video
[QtWebEngine] Saving/Restoring history is now implemented in QtWebEngine
[QWebEngine] Disable use of QWebEnginePage:viewportSize
[QtWebEngine] Fix build with latest QtWebEngine changes