Move to Qt5

Thanks to execjosh <https://github.com/execjosh>
Assume local file if scheme is empty (workaround for weird behavior in QtWebkit. See QWebFrameAdapter.cpp::ensureAbsoluteUrl)
Use new syntax to define JS object's properties
Use new API `toLatin1`
Fix build on Windows

We need to define NOMINMAX due to conflicts with STL
library. See more here: http://support.microsoft.com/kb/143208
Remove text codecs imports.

All text codecs are part of Qt Core now.
Remove ICO plugin
Updated build scripts.
Add libxml to dependencies list
Bump version
Text codecs included in corelib now.
Introducing submodules for qtbase and qtwebkit