Fillers and variables

##
Fillers and variables

The standard CLASS fillers reflect the changes in the Position section. At the Fortran level, the type(observation) is modified as follows:

- obs%head%pos%projang (angle in radians) is added,
- obs%head%pos%system replaces obs%head%gen%typec. Its value remains the special GILDAS code for coordinate systems. Note that obs%head%gen%typec was a convenient duplicate in memory of the corresponding index element, so this affects only the General section in memory, not on disk.
- obs%head%pos%sl0p, obs%head%pos%sb0p and obs%head%pos%sk0p are removed.

At the end-user level, the following SIC variables are affected:

- R%HEAD%POS%PROJANG is added,
- R%HEAD%POS%SYSTEM replaces R%HEAD%GEN%TYPEC and TYPEC which are removed,
- R%HEAD%POS%SL0P, R%HEAD%POS%SB0P and R%HEAD%POS%SK0P are removed,

Finally, for Python-based fillers, the attributes are changed in the same way:

- obs.head.pos.projang is added,
- obs.head.pos.system replaces obs.head.gen.typec,
- obs.head.pos.sl0p, obs.head.pos.sb0p and obs.head.pos.sk0p are removed.