Add support for newcomer month

[dunkOnIT]

Questions:

• Do we want some kind of validation on when to allow newcomer spots to be reserved? I see these options:
  1. [what I'm currently doing] just setting a constant to true/false when newcomer month comps are allowed at all
  2. Setting NEWCOMER_MONTH_START/END_DATE and checking if the comp's {start date/end date?} falls inside that range
  3. Having a boolean on the competition table to mark a comp as a newcomer comp - but I sort of prefer this being implicitly defined by whether or not there are newcomer spots reserved

[dunkOnIT]

Calculate and display the max number of newcomer reserved spots allowed per the 50% WCRP exception limit