Currently transformmap navigator tree has import nodes as direct child of root element.
In case of number of import nodes it isn't comfortable to search required service node through the number of
transformmap root level nodes. It is suggested to add imports container node for transformmap import nodes. More over it
will be inconsistence with bpel navigator.
now:
Transformmap
   import 1
   import 2
   service 1
   service 2

suggested:
Transformmap
   service 1
   service 2
   imports
     import 1
     import 2