gom: Fix sql_type_for_column() return value

Should return NULL not FALSE.
gom: Fix obvious bug in table creation function

There was only ever one command in the creation commands returned.
gom: Fix a memory leak in gom_repository_migrate_sync()

And by extension in the automatic migration sync call.
gom: Fix memory leak when destroying adapter

If we closed the DB properly, we were leaking the queue and thread.
gom: Fix a few memory leaks in GomMemoryGroup
gom: Add to/from bytes metadata properties

If a property is not a number or a string, we'll need help
serialising and deserialising it to a GBytes which we would fit
in a BLOB column.
gom: Use new to/from bytes functions from GomResource
tests: Add test for the new transformation functions
gom: Add GDateTime/strv support in automatic migration
tests: Add test for GDateTime and strv properties