More restructuring around trigger support:
+ Restructure conn values to handle more types of constants.  Add a constant type for trigger columns.
+ Add a trigger table key to hold before/after info
+ Fix casting issue on mariadb.
+ add some helper classes relating to triggers
+ Add planners for triggers for update, delete, insert into select, replace into.
+ Add a TriggerExecutionStep
Intermediate commit:
+ Restructure feature planners slightly to allow for building a plain feature step
+ Initial implementation of update trigger planner
+ Initial implementation of compound statement planner
More trigger support:
+ Add emitter support for late binding constant expressions.  Right now we never swap in actual
  values (because that part doesn't work yet), will have to do more after we have the runtime working.
  Also add support for them in GenericSQLCommand
+ Arrange for trigger bodies to be parsed with the appropriate parser rule when reparsing for planning.
+ Enable support for triggers in trans exec engine.  Add trigger support to transform tests.
+ Modify TriggerExecutionStep to be useful for testing.
+ Restructure the trigger planners slightly to move more functionality into the base class, then
  use it in the derived classes appropriately.
+ Add update and delete trigger planning support.
Merge branch 'master' into kanzaros_cta

Conflicts:
	tesora-dve-core/src/main/java/com/tesora/dve/db/GenericSQLCommand.java
	tesora-dve-core/src/test/java/com/tesora/dve/sql/transform/TransformTest.java