TEIIDDES-1614: Addresses validation error produced by new webservices

* TransformationValidator
 * The if-statement was modified during the 8.2 migration and lost 2 of its
   clauses, resulting in the certainty of firing. The consequence is the
   setting of the projectSymbols collection to empty when it is crucial for
   it to stay null.
 * The if-statement is only necessary for the 7.7.x resolver hence has been
   pushed down into its implementation using the postResolveCommand spi
   method
Merge pull request #117 from phantomjinx/master

TEIIDDES-1614