ENH: Verbosity improvements

[scottclowe]

• save, load, clear, calc_deltaf methods are now verbose (if verbosity>=1).
• More verbosity settings (more verbosity levels, now up to verbosity>=4).
• Progress within an single extraction process can be shown (verbosity>=3), along with which TIFF is being processed (verbosity>=2).
• Amount of time taken is shown when things are finished.
• (With verbosity>=2) the images and rois which will be processed are shown to the user before processing begins.
• With verbosity>=5, joblib becomes verbose as well.

[codecov]

Codecov Report

Merging #238 (938ecbe) into master (ba0680e) will increase coverage by 0.66%.
The diff coverage is 97.23%.

@@            Coverage Diff             @@
##           master     #238      +/-   ##
==========================================
+ Coverage   93.05%   93.72%   +0.66%     
==========================================
  Files           8        8              
  Lines         922     1068     +146     
  Branches      196      248      +52     
==========================================
+ Hits          858     1001     +143     
- Misses         33       34       +1     
- Partials       31       33       +2     

Flag	Coverage Δ
nbsmoke	59.64% <32.04%> (-5.65%)	⬇️
unittests	93.44% <97.23%> (+0.71%)	⬆️

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Impacted Files	Coverage Δ
fissa/deltaf.py	100.00% <ø> (ø)
fissa/neuropil.py	95.16% <33.33%> (-3.18%)	⬇️
fissa/core.py	96.39% <98.31%> (+1.27%)	⬆️

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[scottclowe]

I split off commit ab0860a that was updating the notebooks, so this PR will not interact with #228 now. The update to add a verbosity=2 example to the notebooks will be in a separate PR.