Large redesign of the R2eff/R1rho data structures.

The five indices {Ei, Si, Mi, Oi, Di} for the experiment type, the spins of the cluster, the
magnetic field strengths, the pulse offsets, and the dispersion points (nu_CPMG or nu1) respectively
are now much better defined.  The Oi dimension is new and allows for support of R1rho-type data
whereby both different offsets and different spin-lock field strengths.  Previously only one or the
other was supported, but not both together.  The offset information is now included as part of the
spin R2eff/R1rho key, even if not set.

To support this, the specific_analyses.relax_disp.disp_data module now has the new functions
loop_exp_frq_offset(), loop_exp_frq_offset_point(), loop_exp_frq_offset_point_time(), 
loop_frq_offset(), loop_frq_offset_point_key(), loop_offset(), and loop_offset_point().  All of the
{Ei, Si, Mi, Oi, Di} dispersion indices throughout the source tree have been changed to ei, si, mi,
oi, and di respectively.  And the time index ti has also been introduced.  These changes hugely
simplify the code.