datapath: Refactor actions in terms of match fields.

datapath: Refactor actions in terms of match fields.

Almost all current actions can be expressed in the form of
push/pop/set <field>, where field is one of the match fields. We can
create three base actions and take a field. This has both a nice
symmetry and avoids inconsistencies where we can match on the vlan
TPID but not set it.
Following patch converts all actions to this new format.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Jesse Gross <jesse@nicira.com>
Bug #7115