Princeps Seniores constraints not properly applied

[the-koetjeboe]

Describe the bug
When adding multiple maniples to a Battlegroup, you can add the same number of Princeps Seniores to a single maniple. This also applies to the Legio Vulcanums trait.

To Reproduce
Steps to reproduce the behavior:

1. Create a battlegroup with 2 maniples
2. Make 2 titans in 1 of the maniples a Princeps Seniores
3. Observe the lack of validation error

Expected behavior
I would expect the Princeps Seniores constraint to be properly enforced.

Device and data (please complete the following information):

• OS: Windows
• Release version [v43]

Additional context
The root cause of this is the same as issue #216, maniples are not a Force entry but a selection entry in a Primary Category. This is partly a rereport of #206 in order to track this as still being a known issue.