Create user management functionality (#152)

* Create user management page
* Remove old user creating UI
* Add username validation; admin user auto-creation
* Provide docs on user management
* Bump version

docs/pages/app/ext/user-management.md

@@ -0,0 +1,14 @@
+`ktem` provides user management as an extension. To enable user management, in
+your `flowsettings.py`, set the following variables:
+
+- `KH_FEATURE_USER_MANAGEMENT`: True to enable.
+- `KH_FEATURE_USER_MANAGEMENT_ADMIN`: the admin username. This user will be
+  created when the app 1st start.
+- `KH_FEATURE_USER_MANAGEMENT_PASSWORD`: the admin password. This value
+  accompanies the admin username.
+
+Once enabled, you have access to the following features:
+
+- User login/logout (located in Settings Tab)
+- User changing password (located in Settings Tab)
+- Create / List / Edit / Delete user (located in Admin > User Management Tab)