Fixed missing removal of time information when removing a single key. Plus comment typo fix.
Fixed comments.
Fixed copy/pasta typos in comments.
Moved (de)serialization setup for multi out of the main multi testsuite. Will need different setup for upcoming multitime, forcing the split.
Changed API between mtime core and (de)serialization packages. Simplified, less checking required.
Implemented the multitime feature merger of the multi and mtime classes. Plus tests.