Added color properties to QtPropertyBrowser framework.
selectedTilesChanged signal added to MapDocument.

updateCustomProperties when selected tiles and map objects change.
Added updatePropertyColor in PropertyBrowser.

If selected object does not have property gray out name and value.
If selected object has different value then gray out value.
Update property colors when properties change.

Add properties to browser if current object does not have them.
Merge pull request #779 from parkm/propertyVisuals

Visual feedback for multiple object properties
Silence MinGW warning

libtiled/tilelayer.h:320:20: warning:
'const Tiled::Cell& Tiled::TileLayer::cellAt(int, int) const'
redeclared without dllimport attribute after being referenced with
dll linkage
Updated libtiled Qbs project
Added Qbs files for Tiled plugins

All plugins except the Python plugin for now, which will need a probe.
Qbs: Enabled Python plugin with PkgConfigProbe

Unfortunately, this won't work on Windows and likely not on OS X either.
Qbs: Fixed building of Python plugin on Windows

While hopefully not breaking it on Linux.
Qbs: Fixed Python plugin compilation on Linux

Apparently the probe can't be inside of the Properties.
Make Windows installer on AppVeyor

Based on MinGW. Maybe I'll try adding Visual Studio later.

Also, Tiled is currently failing to compile with Qt 5.4 MinGW so I'm still
using Qt 5.3.
Qbs: Initial support for building translations

Unfortunately the translations are ending up in some product-specific
directory so currently when running a Tiled compiled with qbs the
compiled translation files aren't found.
Lua plugin: Include Tiled version in Lua export

This may help dealing with unintentional differences or doing
workarounds for possible bugs.

Closes #809
Qbs: Build the tmxviewer, tmxrasterizer and automappingconverter tools
Qbs: Specify install locations

Also fixes locating of translations.

Not expected to work on OS X or Windows for now.
Qbs: Use precompiled header

Reduces complete rebuild on Linux from ~40 to ~30 seconds for me.
AppVeyor: Try building releases on tags