Revert "adding ifHCInUcastPkts/ifHCOut"

This reverts commit 3d3f0336229e9f3ad0ec15531258e08162754deb.

Reverted because of comments from Alejandro:

This is really cool but it seems that anyone who is using
storeByGroup won't be able to keep the history of the
statistics from ifXTable because of this ;)

Because of storeByGroup, it is recommended to add metrics
into a different group rather than modifying an existing one.