ENG-7242:  Partial (doesn't address constraints with expressions or
delete statements on limit partition rows).
Fix various broken issues with VoltDB custom constraints and alter
tables:
1) Make sure we copy constraint fields when they're duplicate()-ed
2) Make sure that column checks for Constraint.LIMIT type pass
ENG-7304: Teach HSQL to parse ALTER TABLE statements with constraints
on expressions.
ENG-7305: Allow dynamic ALTER TABLES that affect expression-based
constraints and indexes, but currently only on empty tables.

ENG-7242: Complete the constraint preservation testing for expressions
ENG-7242: cleanup.  I switched up which extension comment went with
which code.
Unreverting an earlier revert.

Revert "Merge pull request #1819 from VoltDB/ENG-7231-revert-ee-limit-execute-delete"

This reverts commit 528f3edb2cfe07e2c64eeba42ab5fd5c91e3bc91, reversing
changes made to f8ef36f3f5ac0c6599e1d10375fcd2274fcfbbbf.

Conflicts:
	tests/testprocs/org/voltdb_testprocs/regressionsuites/sqlfeatureprocs/sqlfeatures-new-ddl.sql
Un-refactor insert executor
Remove unused variable m_partitionColumnIsString and associated dead
code from insert and update executor
Merge pull request #1850 from VoltDB/constraintfixes

Constraintfixes, ENG-7242, ENG-7304, ENG-7305, r=jhugg,cwolff
Back out bad indenting, make new method in insert executor private
instead of protected.
Merge pull request #1855 from VoltDB/cwolff-reintroduce-capped-collections-backend

Reintroduce capped collections backend
added comments and requested constraint test
Merge branch 'master' into ENG-7201-add-new-ddl-statements
Modified alter table add constraint parameters