Changed license to less restrictive Apache 2.0
Added a null check for the UI. It appears that in some scenarios a request can come in late
event when the UI has already been dropped by Vaadin.
Added a null check for the stream variable and security key. It appears that in some scenarios 
a request can come in from the client even though the component has already been detached from
the server side.
Upgrade to Vaadin 7.2.6 and set version for 1.4.4 release.