WIP ENH: Code for updating entities. Also style fixes.

src/Caosdb.m

src/Entity.m

src/Message.m

src/lib/maoxdb.cpp

src/lib/maoxdb.hpp

src/private/getfielddefault.m

src/private/maox_convert_collection.m

src/private/maox_run_transaction.m

src/private/maox_transaction.cpp

test/test_utilities.cpp