Re-implemented missing Zero Portal Lua function

* getAccountsForUser()
* getUsername()
* getVal( name, default )
* isAdmin()
* jsonDecode( value )
* jsonEncode( value, escapeHtml )
* wasPosted()

Change-Id: I8ad0f6253d34ba93b3f6aa3bcbfd42129680be7e
Merge "Re-implemented missing Zero Portal Lua function"