Remove nulls from the syntax layer.
adding tests for union and parenthesized types
Adding support in fidelity for parsing union and parenthesized types
Merge pull request #995 from Microsoft/removeNull

Remove nulls from the syntax layer.
Merge branch 'master' into fidelityParsingUpdates2
Merge pull request #997 from Microsoft/fidelityParsingUpdates2

Adding support in fidelity for parsing union and parenthesized types
Merge remote-tracking branch 'ts_official/master'