Updates to megaplot and adding BW_Flags

1. Adding support for cleaning model
2. Making megaplot python3 instead of 2
3. Log scaling on spectrograms
4. Plasma colomap on spectrograms
5. Support for CBC, full, clean_only, CBC+Glitch, CBC+Signal
6. Cornerplots for signal and glitch models
7. CBC Cornerplots for cbc models

BW_Flags, can now read in BW information into python Call via

    from bayeswave_plot import BW_Flags as bwf

    runFlags = bwf.Flags(TRIGTIME_DIRECTORY)
    bwf.readbwb(runFlags)

Megaplot Examples:

cleanOnly example: https://ldas-jobs.ligo.caltech.edu/~sophie.hourihane/forDerek/ScatteringInjs/H1_MULTIPLE_10/trigtime_8.000000000_0.0_0.0_0/

CBCGlitch example: https://ldas-jobs.ligo.caltech.edu/~sophie.hourihane/glitch_events/BlipLowFreq/BlipLowFreq1/GW150914/August/bliplowfreq1_GW150914/trigtime_1256909978.276999950_0.0_0.0_0/

fullOnly (ie signal + glitch) : https://ldas-jobs.ligo.caltech.edu/~sophie.hourihane/glitch_events/sudarshan/trigtime_1165069535.000000000_0.0_0.0_4/

GlitchOnly: https://ldas-jobs.ligo.caltech.edu/~sophie.hourihane/glitch_events/Whistle/Whistle1/noInj_Dmax300_Niter4e6_window2_srate8192

signal glitch example (separate) : https://ldas-jobs.ligo.caltech.edu/~sophie.hourihane/forNayyer/006_sophie_megaplot/trigtime_1240704078.500000000_0.0_0.0_0/