Expand webUI tests of the User Management page

[phil-davis]

Tests will need to be added here, and then backported into core stable10 also.

Some areas to cover/improve:

• variations of ways to create a user (specifying just email address, just password, adding to groups at creation time...)
• editing user attributes
• selecting/deselecting users in groups
• creating groups
• deleting groups
• selecting a single group on the left panel
• using the various options in the bottom-left tool icon to adjust the page behavior
  ...

[phil-davis]

e.g. cover the bug fixed in #60

[phil-davis]

This app is "sidelined" for now.