Add form validation and toast messages to user mgmt

Adds form field validation with ng-messages and toast messages
with toast service to the User management page. Also adds check
that the number of users does not exceed 15 and that the username
does not already exist prior to sending call to the backend.

Resolves openbmc/phosphor-webui#73
Resolves openbmc/phosphor-webui#74

Tested: Able to add/delete/edit users as before. Page presents
        appropriate message to user upon creating or updating a user
        when:
          1. A field is missing
          2. Passwords don't match
          3. Password is longer than max or shorter than min
          4. Username already exists when creating new user
          5. User tries to create the 16th user

Change-Id: I5ae1a7979f7a396b0fb2ea280b875afc805a7f9f
Signed-off-by: beccabroek <beccabroek@gmail.com>

0 files changed, 0 insertions, 0 deletions