Updated dec_const to use plot_data and plot_func, added optional return for fig and ax objects, updated documentation

Updated meff to use plot_data and plot_func. Now the function output also fig,ax if pl is true. Updated documentation

Updated mpcac function using plot_data and plot_func, added overload for Vector{Corr}, added optional return to plot obj, updated documentation

corr_obs_TMS updated with gaps in measurements and automatic detection of the gaps

t0_phys changed from Bruno et al to the value from internal analysis

corr_obs_TSM now supports different statistics between sloppy and correction without neglecting the correlation. Extra flags idm_corr, idm_sl, nms have been added to allow this feature.
Documentation added

This reverts commit f3531bef.

several functions, needs testing

functions for TSM runs.
read_mesons_correction -> read correction runs (exact + sloppy solutions)
corr_obs_TSM -> create Corr with <O_sloppy> + <O_correction>

Study and preliminary tests  on correlated fits