action: validating number of parameters

The pipeline executor can validate the number of parameters before
executing the action (only if the action declare this value). If the
number is invalid, the executor will switch to backward phase and
rollback completed actions.
app: starting to port to the new action framework

The first action ported is insertApp. I know this code looks like
JavaScript, but we might change it in the future. The renaming approach
is also odd, but I don't want to break the build, neither be unable to
run tests because of broken compilation.

Once all actions get ported, I will remove action.go, action_test.go,
actions.go and actions_test.go, and rename nactions.go and
nactions_test.go to actions.go and actions_test.go, respectively.

It will be a time of bad code, but it's a good reason :-)