Add Obliqua to `proteus doctor` command and PROTEUS version validation scheme

[nichollsh]

Feature description

PROTEUS checks that submodules are sufficiently up to date. When the first release of Obliqua is made, it should also be incorporated into this version checking scheme within PROTEUS.

Preferred solution

Should be straight forward to follow the same approach taken for AGNI, since both are Julia-based codes.

Additional information

Suggested in #669

Relevant people

@MarijnJ0 @egpbos @timlichtenberg