Keeping ordering coefficients from report runcard

[jacoterh]

This PR gives the user more flexibility on the ordering of the coefficients in the barplots (coefficient_bar, coefficient_central, coefficient_pull). Before, the coefficients and groups (4H, 2FB, etc) were ordered alphabetically, which is often not what we want. Instead this PR keeps the ordering as specified in the report runcard, e.g.

coeff_info:
  4H: [
    [OQQ1, "$c_{QQ}^{1}$"],
    [OQQ8, "$c_{QQ}^{8}$"],
    [OQt1, "$c_{Qt}^{1}$"],
    [.... ],
  2L2H: [ 
     [....],
    ]

plots from top to bottom, the 4H starting with OQQ1, the 2L2H, etc..

In terms of plots this means,

this PR:

main:

I have also repositioned the legend.

[LucaMantani]

Looks good and it's a nice control to have!