Fixed linker error on Mac OS X when compiling with Qt 5

Based on Qt Creator commit a4e593c910cca.
Rename tile selection functions in map document.

setTileSelection is now setSelectedArea
tileSelection is now selectedArea
tileSelectionChanged is now selectedAreaChanged
Renamed undo command ChangeTileSelection to ChangeSelectedArea.
Renamed changetileselection.h/cpp to changeselectedarea.h/cpp
Fixed issue with zoom combo box jumping to 1%

Was broken by c6bc0a1e4061cf788342b120e8abcad43064c929. Thanks to
@obeea for finding this.

Fixes #665
Merge pull request #666 from despondentdonkey/refactor

Rename tile selection functions and undo command.
fix DTD: add support orientation="staggered"
Merge pull request #676 from fzzrr/fix/dtd

fix DTD: add support orientation="staggered"
Updated the DTD file included in libtiled-java

This updates the file to the latest version. However, the latest version
of the DTD is still missing years of additions.

Closes #674
Fixed terribly slow object movements with cursor keys

It had not been adapted yet to the switch to storing object positions in
pixels rather than tiles.
Merge remote-tracking branch 'bjorn/master'
Removed pointless layer actions

There is only one layer.
Trimmed more unnecessary stuff