Remove out-dated TODO comment.
Merge branch 'master' into add-union-support
Add a new rules test and new Operators test based upon feedback
Update the test-union.yaml test to remove redundant explains, add new
types casting test.
Create a UnionTypeCast operator.
Move some of the processing for casting input types from
ASTStatementLoader to new UnionTypeCast operator. 

Add Rules test for this specific case.
Merge remote-tracking branch 'github/master' into add-union-support
Add many more tests, various edge cases, odd problems that cropped up
Add a UnionTypeCast to process the Union statements after the TIntance
process has completed but before the rest of the rules. This involves a
fair amount of climbing up and down the operator stack to ensure the
type calculation for the left and right side of the union gets
propigated properly
Update the ASTStatementLoader to insert a Project between the union and
the ResultSet so the TInstanceOverload stop complaining. Make sure the
types and column locations are all correct for this new project.
One more test can't hurt...
Restore exception for unsupported ALTERs
Remove the dead code from the ASTStatementLoader
merge nathanlws: Restore exception for unsupported ALTERs

Merge pull request #1019 from nathanlws/sql-layer/no-alter-add-index
https://github.com/FoundationDB/sql-layer/pull/1019
Rename UnionTypeCast to UnionTypeCaster per review.
merge tjoneslo: Add union support

Merge pull request #1000 from tjoneslo/sql-layer/add-union-support
https://github.com/FoundationDB/sql-layer/pull/1000
Merge branch 'master' into update-version