relax SVN archive

Created the new _pivot_fixed() method for the frame order analysis.

This is to determine if the pivot point is fixed or not during optimisation.

The frame_order.pivot user function now accepts the fix argument to allow the pivot to be fixed.

This is for optimisation.

Fix for the align_tensor.init user function - the tensor name is no longer stored as an alignment ID.

The align_id arg is now used instead, and this prevents problems of multiple tensors defining too
many alignment IDs.

Converted the align_tensor.init user function to accept the align_id and domain arguments.

The domain argument complements the align_tensor.set_domain user function whereas the align_id arg
is new and is used to associate a tensor with an alignment. This is part of a redesign of how
alignment tensors are handled, as there can be multiple tensors per alignment if the molecule is
multi-domain.

The frame order rotor target function can now properly handle missing RDC or PCS data sets.

Fix for the frame order target function class for when RDC or PCS data is missing.

Fix for the rotor frame order model for when either RDCs or PCSs are missing.

Removed the full output of the scipy.integrate.quad() function for a slight speed up.

Pre-calculation of a dot product to speed up numerical integration of the rotor frame order PCS.

The frame order rotor model should now be functional with RDC and PCS data together.