Fixed bugs of previous theorycovariance runcards and added new working runcards

Created by: andreab1997

Fixes issues #1519 (closed) and #1521 (closed) . Note that

1. The flags fivetheories and seventheories are not used anymore in the runcard. The wanted prescription must be specified in point_prescription instead. Anyway the point_prescription : '7original point' and point_prescription : '5linear point' will not work because they are not implemented in validphys2/src/validphys/scalevariations
2. Since the correct theoryids are now loaded directly by https://github.com/NNPDF/nnpdf/blob/9840fc69dfcbcf25ebb30236916c4f1fc65a1785/validphys2/src/validphys/config.py#L1515 the dataspecs entry in the runcard seems to have no use. Anyway, since it could be used by other functions, maybe we should add a check to be sure that it corresponds to the correct point_prescription.
3. The covariance_matrix_plots family of new runcards uses a new template (template_matrix_plot_new) which does not include some of the functions of the original one. That is because the issue #1520 (closed) has not been solved yet.
4. All the default values of point_prescription, fivetheories and seventheories have been removed.
5. Most of the previous bugs were caused by an incorrect order of arguments in some function calls.