Remove old modules (sph, Metafor, fdtd)

Since this repository is going to be frozen soon and replaced by several new ones such as amfe, dartflo, one repo to be created for heat/waves and another one for Kim's work (mirrors/katoptron/params), it is important to remove the parts that are not related to the "waves/fwk" structure from this repository.

The following folders have been removed:

• sph: moved to https://github.com/rboman/progs/tree/master/classes/sph0
• Metafor: archived with my "old scripts to be refactored"
• fdtd: moved to https://github.com/rboman/progs/tree/master/classes/fdtd