Removed methods getReference and getTransactionHandlerClass from
Interface PendingCommandFactory.
This simplification implicited a simplification of
SimplePendingCommandFactory, where Parameter reference is removed from
the constructor - and removal of implementations of getReference and
getTransactionHandlerClass.
The removal of Parameter reference implicited instantations of
SimplePendingCommandFactory.

Signed-off-by: Jakob Brandsborg Ehmsen <jakobehmsen.github@gmail.com>