meshManager can now handle height but there is an issue when used with n...

when using negative height, can't realy explain this have to be see.

meshManager have to be keep alive since it keep track of generatedMesh. Added to MapSpatialAppState
There is an issue with MapSpatialAppState at line 94 he can't get in that statement, leaved as is to avoid conflict.
Corrected the gap issue since if the value is < than the real hexSize it make face overlap realy badly, not so cool. Added comment on it since it could be usefull later on.