Progressing Cavity Pump (cycloidical)

**Note: Use of this code is DEPRECATED**

Generating this progressing cavity pump thing that is presented here can
now be done with just a few lines of code by using the new library:
http://www.thingiverse.com/thing:777936
https://github.com/lsuess/scad-lib-cyclogearprofiles

Here is a similar (followup next version) progressing cavity pump thing where that new library is used.
http://www.thingiverse.com/thing:867401

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DESCRIPTION:

This is the center part of a progressing-cavity-pump (PCP-pump or moineau-pump)

It implements the design approach with alternating epi- and hypocycloids which avoids cusps/kinks (the curve is C1 but not C2 continous)

Right now it uses two and threefold symmetry for rotor and stator respectively, but it shouldn't be hard to change it to any N and (N+1) symmetry (it's prepared) like three and four for more sturdiness or one and two for more throughput.

It is a positive displacement pump and thus provides (if t