TEIIDDES-2118: Display error message when jdbc connection fails

* ExecuteVdbWorker
 * Display the error dialog if the code of the connection's returned status
   is ERROR.

* TeiidJDBCConnection
 * Breaks up the exception handling to differentiate between a
   ClassNotFoundException which should be ignored and an actual connection
   failure which needs to be thrown and reported to the user
TEIIDDES-2118: Factor out all connectivity plugin's message strings

* Uses enums in Messages class to refactor all exception messages into
  separate resource properties file