Combine the post DL3 notebooks, to solve few minor issues

[chaimain]

The LC was not produced appropriately, by providing any custom energy range, as gammapy required the flux points edges to be the same as the "energy" axis (used for the events) provided while creating the SpectrumDataset.

So, to keep the process uniform, I combine the 3 notebooks, back into a single notebook, where the energy range for LC estimation depends on the energy edges of the energy_axis. Also, energy_axis and energy_fit_edges have the same edges.

Other changes are -

• Option of applying custom safe energy masks, in blocks 19 and 20, instead of using SafeMaskMaker
• Small fix on displaying (or saving) the various plots of each dataset (counts+excess, exposure and energy dispersion) in block 25, to avoid issues when having large datasets.
• OGIP files are still written, but not used in this example to produce LC and SED. They can be used easily, but for further simplicity, I avoid doing so here.
• After performing the Fit function, using the updated spectral model parameters, for estimating the LC from the dataset
• Storing the Optimization results along with the final model into a file, in blocks 44 and 56
• In block 57, I save the flux points tables of SED and LC data as HDUs in a fits file, and in the final blocks, show how one can use the fits file to reproduce the LC and SED. This fits file is not based on GADF standard, but just a temporary usage, where we can compare the results of different analyses (or sources if need be).

I request analyzers to review and check if there is a need for some more modification or information in this general example notebook.

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[gabemery]

Very good notebook but I still had a couple of comments. Some of them need to be solved before merging.

It seems like your build is failing due to "lstchain_longterm_dl1_check" which is weird.

[codecov]

Codecov Report

Merging #955 (7dd6700) into master (b1f83fa) will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #955      +/-   ##
==========================================
+ Coverage   85.46%   85.49%   +0.03%     
==========================================
  Files          78       78              
  Lines        6461     6461              
==========================================
+ Hits         5522     5524       +2     
+ Misses        939      937       -2     

Impacted Files	Coverage Δ
lstchain/reco/r0_to_dl1.py	93.67% <0.00%> (+0.63%)	⬆️

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[maxnoe]

Shouldn't the original notebooks also be removed?

[chaimain]

Shouldn't the original notebooks also be removed?

Ah Sorry, I thought I had done so.

[gabemery]

Latest changes look good. I didn't go over previously reviewed code again. I think you can merge.