IMPALA-849: Impala does not work with boolean partition key columns

This is because in HdfsTable we call call "expr.castTo(colType)", but BooleanLiteral
(incorrectly) didn't implement "uncheckedCastTo()". This meant that instead of a
BooleanLiteral being returned we got back a CastExpr, which cannot be cast to LiteralExpr.

As part of this change it turns out Boolean partition columns are also broken in Hive. I
filed HIVE-6590 for these issues and we decided to disable INSERT into a boolean partition
column for Impala due to this bug.

Change-Id: I3e295bb96aadc08d64faf551f6393a7128a7ef27
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1755
Reviewed-by: Lenni Kuff <lskuff@cloudera.com>
Tested-by: jenkins