Added python wrappers for ObjectGroup::objectCount() and ObjectGroup::objectAt(int index) methods
Reordered generated code to make changes smaller
More methods getters and setters wrapped (name, isVisible, rotation)
Added a semicolon to the tiled.desktop file

As reported by 'desktop-file-validate' on openSUSE Build Service:

error: value "application/x-tiled-tmx" for string list key "MimeType" in
group "Desktop Entry" does not have a semicolon (';') as trailing
character
Merge pull request #554 from ajuc/branch_to_pull_mappings

Wrapping more methods of MapObject and ObjectGroup in Python to make it possible to use them in Python plugins.
Make highlighted grid cells outside map red
Added Python bindings for type() and setType(str) on MapObject.
Python plugin cleanups

Mostly about coding style.
Fixed Map::clone to also clone background color and layer data format
Python plugin: Fixed several memory management issues

* Fixed a problem with using a function call as argument to Py_XDECREF,
  introduced in my recent cleanup. Due to this being a macro the function
  call was done twice, leading to a crash due to accessing null-pointer.

* Provided a proper copy constructor for Tiled::Map because the generated
  Python relied on it. The default copy constructor was not deep-copying
  map layers, leading to a double-free when the maps were being deleted.
  This avoided the need to keep around references to loaded maps as well
  as the need to clone a map before saving it.

* Don't manually delete references to plugin modules, classes and the
  reference to the Tiled Plugin class. Python doesn't like that so now
  references are decremented as appropriate before calling Py_Finalize.

Some problems seem to remain since valgrind wasn't entirely happy yet,
but I hope it will not crash as often now.
Set the ownership of the MapsDock file system model instance

Poor orphan wasn't being deleted.
TMX: Save width/height of individual tile images

Useful in case somebody wants to process the file without loading the
images but still wants to know the size of the tiles. Tiled currently
does not use this information.

Closes #538
libtiled-java: Fixed warnings and added annotations