Emit FIRRTL andr, orr for Bits.{andR, orR}

Change the emission strategy for Bits methods andR and orR to emit
FIRRTL bitwise reduce operations andr and orr.

Add two tests that assert the correct behavior of these operations in
BitwiseOpsSpec.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>