This follows from http://thread.gmane.org/gmane.science.nmr.relax.devel/4530, the thread about
supporting multiple data types such as SQ+MQ data simultaneously.
The logic for the page ordering needed to be changed to be more dynamic. The CPMG and R1rho pages
need to be shown only if the corresponding experiment type exists in the current data pipe. Hence
the has_cpmg_exp_type() and has_r1rho_exp_type() dispersion functions are now used by the new
methods wizard_page_after_relax_time() and wizard_page_after_cpmg_frq(). A number of now useless
flags have also been removed.
