also enable to add tidal velocity to Tangential Flow

To also test the addition of tangential component of the tidal velocity,
import the updated set-up from @antnguyen PR MITgcm#73 (branch "obcs_tides_tangential")
including updated ref output from the same PR.

Allow to provide tidal Ampl & Phase bin files with just the number of tidal-comp
that are used (instead of the full tidal-comp size "OBCS_tideCompSize") by
calling directly pkg/msdio section-read S/R.

And provide some instruction on how to update previous data.obcs
to work with this updated code.