feature allow group max_size editing

group max_size editing added to group in admin panel

migration to update max_size for recently  groups

remove group new route and spec

add extra check on model for populating max_size

schema no-change

Remove redundant cuc specs

Add validators on maxsize
Merge branch 'master' of github.com:enspiral/loomio into feature/admin-panel

* 'master' of github.com:enspiral/loomio:
  Add better error for development
  Fix request new group button on homepage.
  uncommented close_date in mailer
  text changed from dashboard to home page
Fix 'create a group link'
Merge pull request #451 from enspiral/feature/admin-panel

group max_size editing added to group in admin panel