Slight refactor for reuse
Select from i_s and ddl MT
Add Session to MemoryTableStatus#rowCount().

Tighten synchronization in MemoryTableStatus.

Remove unimplemented methods from MemoryAdapter interface.

Allocate RowDefCache when needed in SchemaManagers.
Rename RowDefCache to RowDefBuilder
Remove dead code from RowData
Remove dead/unused code from FieldDef and RowDef
Disable test for now
merge nathanlws: Cleanups to RowDef and associates

Merge pull request #1287 from nathanlws/sql-layer/no-row-def-cache
https://github.com/FoundationDB/sql-layer/pull/1287