Move showPanel function into sidePanel directive.
Code cleanup.
Convert userSettingsPanel HTML content into panels.

* Add /template/users to contain HTML templates,
* Add directives for each HTML content piece,
* Move HTML content out of <user-settings-panel> HTML tag to display independently
Update links to trigger the new panels.
Add formValidation factory to keep track of errors.
Track for changes in formValidation, in formErrors directive.
Use formValidation methods.
Fix typo in formValidation variable
Minor code cleanup.
Deprecate serverError, and message, and update formValidation service.
Use formValidation for loginForm directive.
Use formValidation service for sidePanel directive.
Use formValidation for userSettingsPanel, and userActionsForm.
Minor code cleanup.
Add hack to deal with cases when username is not passed in form.

TODO: We definitely need to fix this, but a hack suffices for now, unfortunately.
Code cleanup.