Groups app frontend validations and alerts

[rorysaur]

In the Groups app create/edit form:

1. Name cannot be blank.
2. Member IDs cannot be blank.
3. Member IDs must be in the correct format (comma-delineated strings) AND each member ID must correspond to an existing member. (This entire validation will be unnecessary once Add autocomplete to add members to a group by name #30 is completed.)

Validate these on Save.

1. If all validations pass and the save is successful, there should be an alert below the Save button saying:
   a. for create: "Your group has been created! [View your group.] (with link to the group's View page)"
   b. for edit: "Your changes have been saved! [View your group.] (ditto)"
2. If any validations fail:
   a. There should be an alert below the Save button saying: "Something went wrong. Check for errors above."
   b. There should be a message below each failing field specifying what the problem is.
3. If all validations pass but the save fails for any reason, there should be an alert saying: "Something went wrong." with the error message appended if there is one.

Additionally, gray out and disable the Save button while waiting for the save.

See the Adventures create/edit form (ProjectForm) for examples of all of the above, including per-field validations and validation messages, success and error alerts, how to link to the new entity's page, and disabling the Save button.

[thestrabusiness]

Will take a shot at this!

[thestrabusiness]

Got a draft PR opened just now. Still need to clean some things up which I should be able to take a shot at tomorrow evening.