Limit the number of groups that can be created in an institution

When a site is used for multiple institutions, it would be good for the site administrator to limit how many groups can be created within an institution, similarly to how they can set a maximum number of accounts. That will help administer the site more easily without needing to do any manual checking.

1. Add a setting 'Maximum number of groups allowed' below the setting 'Maximum number of accounts allowed' on the institution settings page.
2. That setting shall only be visible to site administrators like 'Maximum number of accounts allowed' so that institution admins cannot change it.
3. That setting shall not be available for 'No institution'. There is no limit on how many groups can be created in 'No institution'.
4. Add two columns to the overview page for the institutions at Admin menu -> Institutions -> Settings:
  - Groups
  - Maximum number of groups
5. Change the 'Maximum' column heading to 'Maximum number of members' to differentiate it from the groups.
6. When someone tries to add a group to an institution that has reached its limit, either via manually creating a group, copying a group, or bulk uploading groups, have an error message along the lines of:

a) single group is created from Main menu -> Engage -> Groups and also when group is copied:

This group was not added because the maximum number of groups allowed in this institution has been reached. Please get in touch with your [institution administrator](/institution/index.php?institution=APPROPRIATEINSTITUTION) for next steps.

b) bulk group creation in Admin menu -> Groups -> Add groups by CSV:

The group creation failed because the maximum number of groups allowed in this institution has been reached. Please get in touch with the site administrator to discuss raising the limit.