making rocks unbreakable as workaround for issue #114 for now.

Conflicts:
	love2d/game.lua
giving the player some mass at the start so he can build some towers
fiddling around a bit with the values
added some siren music to the intro
finally found the culprit
used some water
Merge branch 'develop' into feature/issue/#84_Tutorial_level

Conflicts:
	love2d/data/map/tutorial1.ini
some initial tutorial level layout
Merge branch 'origin/feature/issue/#63' into feature/issue/#84_Tutorial_level

Conflicts:
	love2d/data/map/tutorial1.ini
first two waves do what I want them to, for now
syntax error
Revert "syntax error"

This reverts commit 55c74abfd9351a6006d737acd0ef9c89cad1e9f9.
rename filename endings from .ini to .lua (so that I can more easily format them in Eclipse)
reformat
Polish intro, countdown, start message.
preparing to add more waves
experimenting with the values
Merge branch 'develop' into feature/issue/#84_Tutorial_level
roughly this tutorial structure is fine for now
Merge branch 'feature/issue/#84_Tutorial_level' into develop