Simplified use of zlib with Qt 5 on Windows

In fact Qt Core is still exporting the zlib symbols, but the symbols
are prefixed now. To use them QtZlib/zlib.h needs to be included.

No need to install zlib separately, yay!
Merge pull request #594 from mauvecow/multipletsxload

Allows adding multiple external tilesets at once.
Merge pull request #597 from mauvecow/maprendererscale

Adds painterScale to MapRenderer to fix shadow offset issues for rotated objects.
Added tile animation editor

Allows editing tile animations by drag & drop.
Implemented deleting of tile animation frames
Added option to disable playing of tile animations
Made undo/redo shortcuts work in tile animation editor

Also update the frame list as appropriate and make sure only one undo
command is created when deleting multiple non-consecutive rows at once.
Made animated tiles recognizable in the tileset view

By rendering a film strip on top.
Lua plugin: Support tile animations and image collection tilesets
JSON plugin: Added support for tile animations
Merge pull request #591 from mauvecow/screencoords

Renamed "pixel" to "screen" coordinates and introduced a new "pixel" coordinate type.
Merge pull request #592 from mauvecow/mapobjectunitsv2

Map Objects' internal representation converted to pixel units
Fixed snapping to grid when moving and pasting objects

When pasting objects it was dealing with pixel coordinates rather than
tile coordinates for aligning.

For the moving, the alignment position is now in pixel coordinates but
was still treated as being in tile coordinates.
Converted old map object resizing code over.
Supported resizing in IsometricRenderer.
Can now resize single polygons.
Corrected scaling of polygons on multiple selections.
Corrected snapToGrid behavior in objectselectiontool.