The atoms of all standard amino acids are defined in a RotamerLookup class.
This class has three different modes and defines amino acids accordingly:
HEAVY_ATOM_MODE, POLAR_HYDROGEN_MODE, FULL_ATOMIC_MODE
The RotamerConstructor makes sure that all the atoms defined in the
RotamerLookup are stored in position buffers when constructing
rotamers/frame residues.

The actual Particle parametrization happens in an energy function specific
child class of RotamerConstructor that has access to the position buffers
and some additional information to parametrize the constructed particles.
It also determines what mode in the RotamerLookup of the parent class is
used.

The motivation was to move as much away from the child class in order to make
it as easy as possible the add new energy function specific child classes of
RotamerConstructor.

The new implementation does not exactly reproduce the results from before
(but almost), as there have been introdued minor changes / bugfixes.

- The construction of terminal hydrogens / oxygens is more sane
- CB of HSD previously ended up in the sidechain, the default should be backbone frame
- GLY CA is of SCWRL4ParticleType CH2Particle, not CH1Particle