Feature/allow custom matplotlib backend

[prasad-sawantdesai]

Allow user to use matplotlib backends

List of backends

['gtk3agg', 'gtk3cairo', 'gtk4agg', 'gtk4cairo', 'macosx', 'nbagg', 'notebook', 'qtagg', 'qtcairo', 'qt5agg', 'qt5cairo', 'tkagg', 'tkcairo', 'webagg', 'wx', 'wxagg', 'wxcairo', 'agg', 'cairo', 'pdf', 'pgf', 'ps', 'svg', 'template']

plotequilibrium -u  imas:hdf5?path=/work/imas/shared/imasdb/ITER/3/100507/5 --md "imas:hdf5?path=/home/ITER/hoeneno/public/expdata/ITER/MD"  --rc "backend='qtagg'"

idsprint  -u "imas:hdf5?path=/home/ITER/tribolp/Public/imasdb/predictMagnetics/3/135011/from_efitpp_noise#pf_active/coil[10:13]/current/data" -p --rc "backend='pdf'"

[olivhoenen]

LGTM, we will need to remember to set MPLBACKEND=TkAgg into the EB module for IDStools, so it overcomes the annoying MPLBACKEND=Agg

[SimonPinches]

LGTM, we will need to remember to set MPLBACKEND=TkAgg into the EB module for IDStools, so it overcomes the annoying MPLBACKEND=Agg

We can also change the MPLBACKEND that's set in the matplotlib module if desired (or instead).