Instead of SCAnnotate trying to find vector loops, the routine that
creates them marks them with `!$loki vector`, which SCCAnnotate
then translates to OpenACC pragmas.

This also uses in-place updates in SCCAnnotate now to speed up
processing.

A small bit of refactoring of the `SCCRevector` core routine also
ensures that we now only detect `!$loki loop seq` loops inside
driver-loops.

This also renames and refactors the `check_routine_pragmas` utility,
which now only needs to check for genuine `!$loki routine seq`
annotations.

We also change the static classmethods to regular methods to
provide acces to the `directive` property in the follow-up.

Theres' a subtle bug, where they can be attributed to the body,
and thus need moving explicitly. This was done by the provious
utility, but never checked explciitly - so now we do test it!

Adds a small test and does not print data clauses if no arrays
are passed to the routine.