Add more context-sensitive keywords

Use Sequence.flush() in AlterSequence to avoid concurrent update exception

Fix concurrent deletion handling in SELECT FOR UPDATE

Assorted changes

Fix DISTINCT ON in presence of ORDER BY

Fix window functions in JOIN with ON condition

Add transparent key to Console tool that unlocks creation of new databases

Fix ConditionInSelect used as JOIN ON condition

Bug fix and tuneup for MVMap.tryLock()

Add DATABASE_TO_LOWER and CASE_INSENSITIVE_IDENTIFIERS