Plotting issues in Likelihood

[jasercion]

As of the most recent fermitools release (Fermitools 2.4.0) plotting within likelihood (calling gtlike with the plot=yes parameter) no longer throws a core dump/seg fault on MacOS machines but continues to be a problem/display the same behavior on Linux machines.

This issue will act as a superseding catch-all for all plotting related updates with regards to the likelihood package. Previous issues will be pointed here as well and developer updates and comments on this topic will be posted here moving forward.

[jasercion]

Matplotlibcpp is now compiled without a compile-time dependency on Numpy. The issue still persists on linux machines, however, this removes one potential complication