Implementation of A/E fit background function with two EMGs

[verenaaur]

changed so far:

• changed markersize in plot recipe
• implemented option to choose between aoe fit background function with one EMG (default) or two EMGs (-> two fit_func 'aoe_one_bck' and 'aoe_two_bck')
• updated plot recipe: additional keyword "x_label" which is set to "Energy (keV)" by default; show A/E labels by using "x_label = "A/E"" like this:
  p = plot(report, x_label="A/E")
• updated A/E pseudo priors (still some LogUniform distributions, though)
• updated A/E fit function (two EMGs) in peakshapes.jl file to include sigma = 0.0 case

current code to obtain Compton band histogram (when 'filtered_aoe' is the array with all the filtered aoe values of the CBs):

binsize = 0.05
h = fit(Histogram, filtered_aoe, -20:binsize:3)
ps = LegendSpecFits.estimate_single_peak_stats_psd(h)
result, report = LegendSpecFits.fit_single_aoe_compton(h, ps, fit_func=:aoe_two_bck, uncertainty=true) # use background function with two EMGs
p = plot(report, x_label="A/E") # use A/E labels instead of energy labels

(binsize 0.05 and interval [-20,3] is variable)

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 54 lines in your changes missing coverage. Please review.

Project coverage is 21.85%. Comparing base (02da7b0) to head (5e32899).
Report is 38 commits behind head on dev.

Files with missing lines	Patch %	Lines
ext/LegendSpecFitsRecipesBaseExt.jl	0.00%	27 Missing ⚠️
src/aoefit_functions.jl	0.00%	13 Missing ⚠️
src/aoe_pseudo_prior.jl	0.00%	5 Missing ⚠️
src/peakshapes.jl	0.00%	4 Missing ⚠️
src/aoefit.jl	0.00%	3 Missing ⚠️
src/aoefit_combined.jl	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev      #77      +/-   ##
==========================================
+ Coverage   15.11%   21.85%   +6.73%     
==========================================
  Files          32       33       +1     
  Lines        2680     2970     +290     
==========================================
+ Hits          405      649     +244     
- Misses       2275     2321      +46     

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[theHenks]

Some minor changes, then we can merge.

[theHenks]

Let's catch also here the case for sigma = 0.0 similar to the energy peakshape. Otherwise we might run again into numerical instabilites.