Global lattice parameter computation

Some of the global computations we want to do include tune computation and orbit stability computation.

There are a number of different tune finding algorithms available in AT.
These may all be accessed with the function
findtune_multi
[tune,spectrum]=findtune_multi(pos,method)
Here, pos is the tracking data and method may 1-4 which represent
'highest peak', 'interpolation', 'window + interp.', and 'naff' respectively.

The tune at different initial positions may be computed using the function atnuampl
function [nux,nuz]=nuampl(ring,ampl,xz,pl)