Add a setting to force image output format

[kdm9]

It seems that sigal uses the format of input images for each output image. This new setting allows one to hard-code the output format of all images in the settings.conf.py.

My use case: I develop images to tiffs, and many browsers dont' like tiffs it seems. Now I can force JPEG output for all images, and browsers are happy to display them.

Thanks,
Kevin

[codecov]

Codecov Report

Merging #360 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #360   +/-   ##
=======================================
  Coverage   87.41%   87.41%           
=======================================
  Files          18       18           
  Lines        1438     1438           
=======================================
  Hits         1257     1257           
  Misses        181      181

Impacted Files	Coverage Δ
sigal/settings.py	97.87% <ø> (ø)	⬆️
sigal/image.py	92.22% <100%> (ø)	⬆️

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[codecov]

Codecov Report

Merging #360 into master will increase coverage by 0.06%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #360      +/-   ##
==========================================
+ Coverage   87.42%   87.49%   +0.06%     
==========================================
  Files          19       19              
  Lines        1503     1503              
==========================================
+ Hits         1314     1315       +1     
+ Misses        189      188       -1

Impacted Files	Coverage Δ
sigal/settings.py	97.87% <ø> (ø)	⬆️
sigal/image.py	92.22% <100%> (ø)	⬆️
sigal/plugins/watermark.py	88.37% <0%> (+2.32%)	⬆️

---

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[kdm9]

(WORK IN PROGRESS)

[saimn]

This should be commented as this file is meant to be used with the default values when creating a new gallery. Could you also add in the comment a list of possible values for the most common formats (e.g. png) ?

[saimn]

Thanks, this can indeed be useful. If you can address my comment then I think it is good to go ?

[saimn]

Thanks!