OMUSE doc reorganization

[ipelupessy]

OMUSE docs need to be expanded and reogranized

• [ ] general framework documentation
• [ ] utilities and extension doc
• [ ] move dales and era5 to codes section
• [ ] add to codes section
• [ ] examples section ?
• [ ] make sure install instructions are correct
• [ ] resolving common problems section

[ipelupessy]

install instructions are not entirely correct #62 and install of amuse-devel.