Rework of user account commands

Rework of user account commands to make them work as expected
Additional checking and 'smarts' for all commands
Add 'enable user' command as a companion to the delete (disable) user
command available.
Add 'disable user' for simple disabling of accounts
WebUI viewer graphics (Issue #30)

Reformatted the thumbs for Firestorm, Phoenix, Voodoo & Zen for a
consistent background and size.
Updated graphics for Firestorm & Phoenix
Added Firestorm css codes to all current styles
Move Library UUID definitions to Constants (Issue #19)

Move  the LibraryOwner and LibraryRootFolderID UUID definitions to
Constants to allow for easer usage in the WebUI.. and future
maintainability.

Update UserAccountService to use the new constant definition in checks
Update WebUI to ignore system users (Issue #19)

Update WebUI to ignore system users, (currently the Library Owner) in
the user  online, search and profile pages