remove unused methods in HashCache
add JoinStatement and related classes
add comments for SubqueryJoinTableNode
modify SQL lexer for joins
modify join compilation
add HashJoinPlan
add more implementation to QueryCompiler
fix conflicts
fix compilation
Add leading TENANT_ID PK column to SYSTEM.TABLE and make existing CreateTableTest pass.  Most other tests still hosed.
Fix tenant-specific drop table.  Tests for tenant-specific table creation and destruction.
Don't create physical HBase table for tenant-specific table creation.  Tests to verify that behavior.
New test for tenant-specific tables.  Upsert hangs.  Urgh.
Add more querycompiler impl
Complete QueryCompiler for joins
Fix UT regressions
fix unit test
add post join filter in runtime
add subquery extraction implementation in JoinCompiler
add JoinCompiler impl