Second Component Flag

[Jojendersie]

Add an inner/outer flag in addition to solid

• nothing can be attached to outer components
• visibility determination: based on solid like now, but without connector determination
• if one is inner use connector

[Jojendersie]

A second flag causes a lot of changes anywhere. The voxels would need to store more -> more memory and more small bugs. Observations:

• If an inner component uses a connector the outer needs one too (otherwise rendering bug)
• An outer component can never be invisible (thus all the solid stuff is useless for this component)

So I decided to replace the "solid" by the "inner" flag. The only evolving restriction is that any component needs a solid connector (not sure if there is another possibility at all).