[ts.util.validation] remove old validation stuff

We don't use it, and it's in the git repo now anyway if we need it.
[test_parse] tests for date parsing & api change
[ts.parse] misc fixes

Fix a badly named function call, and make some variables more logcically
named
[ts.parse.validate] correct exception name in docs

s/MultipleInvalidError/MultipleInvalid/g