relax SVN archive

Removed unused imports.

This is from the splitting of the specific_analyses.frame_order.uf module into the new geometric
module.

Removal of a tonne of unused imports in the lib.dispersion package.

These were identified using the command "pylint * --disable=all --enable=unused-import".

Updated the numpy version requirement to be >= 1.6 on the http://www.nmr-relax.com/download.html webpage.

Updated the numpy minimal dependency in the installation chapter of the manual to version 1.6.

Numpy version 1.6 or higher is now required to be able to run relax.

This follows from the series of messages:

- http://www.mail-archive.com/relax-devel@.../msg06288.html,
- http://www.mail-archive.com/relax-devel@.../msg06289.html,
- http://www.mail-archive.com/relax-devel@.../msg06327.html,
- http://www.mail-archive.com/relax-devel@.../msg06335.html.

If too many users complain, maybe this change can be reverted later. This minimal numpy version is
needed for many of the speed ups going in the relaxation dispersion and frame order analyses. It is
required for the numpy ufunc out arguments and for the numpy.eigsum() function. These will likely
be used in other analyses in the future for improving the speed of relax, so it might affect users
of other analyses later on.

A very small speed up to the CR72 dispersion models by minimising repetitive maths operations.

The k_BA and k_AB rates are used to simplify the Psi calculation, dropping from 3 to 2
multiplications and removing a squaring operation. The Dpos and Dneg value calculations have been
simplified to drop one multiplication operation. And the calculation of eta_scale / cpmg_frqs now
only occurs once rather than twice.

Using the disp_profile_all.py script, the speed ups for these two models are:

100 single spins analysis:
CR72: 1.608+/-0.025 -> 1.552+/-0.028, 1.036x faster.
CR72 full: 1.795+/-0.043 -> 1.705+/-0.024, 1.053x faster.

Cluster of 100 spins analysis:
CR72: 0.109+/-0.001 -> 0.107+/-0.001, 1.026x faster.
CR72 full: 0.114+/-0.004 -> 0.110+/-0.001, 1.034x faster.

Shifted the rotor generation for the frame order geometric representation into its own function.

This is the specific_analyses.frame_order.geometric.add_rotors() function which adds the rotors are
new structures to a given internal structural object. The code has been extended to add support for
the double rotor model.

Replaced all self.num_frq with self.NM in target function.

Task #7807 (https://gna.org/task/index.php?7807): Speed-up of dispersion models for Clustered analysis.

Replaced all self.num_exp with self.NE in target function.

Task #7807 (https://gna.org/task/index.php?7807): Speed-up of dispersion models for Clustered analysis.

Replaced all self.spins with self.NS in target function.

Task #7807 (https://gna.org/task/index.php?7807): Speed-up of dispersion models for Clustered analysis.