Task repeat count, better tile collisions, bug fixes

* Tasks (if in repeat mode) can be given a repeat count value with
.setRepeatCount(int). This makes it possible, for example, to use the
Scheduler framework for iterating over an array with delays in between
each iteration. Due to this change, tasks now also provide the amount of
'task ticks' in addition to 'total ticks'.
* Tiles can now be given coordinates and a Level instance on collision,
which makes them able to react to collisions better. This removes the
workaround I added to make last Ludum Dare's game possible.
* Tiled levels now correctly translate screen coordinates into tile
coordinates when result is less than 0.
* The methods for drawing textures now take doubles instead of ints, so
you do not have to do the casting. This adheres to the ShapeRenderer
standard.