Exposed `shapes` in the documentation

so that we can enforce the direct usage of `shapes` rather than the
`getShape()` function
[#438] simplified a bit the code parsing the tileset properties

thanks Jason for pointing this out ;P
[#438] renamed this function now that we only have one parser
Merge branch '1.1.0-dev' of https://github.com/melonjs/melonJS into 1.1.0-dev