Invitations: added more columns to table, increase complexity of random invitation string.
Invitations: added DateExpires column to table.
Core: added option to toggle sending email in Save method. This is so that the importer can continue to toggle email sending for both insert and invite modes, particularly for debugging purposes.
Core: updated UserModel's InsertForInvite method to handle custom expiry dates and roles.
Merge branch 'stage' of github.com:vanillaforums/Garden into feature/invitation-improvements
Make password match checking a bit more robust.
Tweaks to invitation db structure.

- Remove banned column.
- Index some additional columns.
Improve invitations:

- Make /entry/registerinvitation always work.
- Fix expiration checking.
- Allow invitations to be deleted after being accepted.
- Sort invitations by reverse date inserted.
- Make some of the /profile/* invitation endpoints do a POST instead of get.
Fix the registration options in the dashboard settings.
Switch InvitationModel->Save() to have an options array. Also fixes the bug where invitations are not sent when inviting through the ui.
Fix negative invite expiries that have been saved to the config.
Merge branch 'stage' of github.com:vanillaforums/Garden into feature/invitation-improvements