BUG-2459: Reuse SAXTransformerFactory in EXI decoder

Rather than allocating the same factory over and over, create a single
instance for reuse.

Change-Id: Ia615dbd462527addadb03a5f2e54618438fb1612
Signed-off-by: Robert Varga <rovarga@cisco.com>
BUG-2459: optimize NetconfOperationRouterImpl operations

Ensure operations are created immutable at initialization, thus removing
the need for synchronization and speeding up lookups.

Change-Id: I26ca5aba435d989689994364c53b4d27c7eccd84
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge changes I26ca5aba,Ia615dbd4

* changes:
  BUG-2459: optimize NetconfOperationRouterImpl operations
  BUG-2459: Reuse SAXTransformerFactory in EXI decoder