added segmentation relabeling.

[twongjirad]

For issue: #73

[twongjirad]

Basic relabeling map given in example config file: segmentrelabel.cfg.

Also, I took the liberty of making a README file for the ImageMod folder. There are a lot of processors in there. Would be nice to have documentation. Added some basic documentation for new SegmentRelabel module in this README. Would be nice to update this with information for the rest of the modules.

I confirmed this work by simple eye-test. I didn't check accuracy of relabeling.

ORIGINAL LABELS

RELABELED

[twongjirad]

Sigh. SegFiller module already does this, maybe...

[drinkingkazu]

SegFiller allows to re-define map on the fly, avoiding to remaking segmentation image.
There are two cases for re-labling segmentation maps imho:
0) Fixing incorrectly labeled segmentation map

1. Interfacing with outside software (like caffe) and map the larcv segmentation map to theirs

SegFiller is for 1). SegFiller does not store segmentation map because I think it is confusing to have a segmentation label map with values different from what is defined in enum.
I think this module can be useful for 0)?

[drinkingkazu]

Yeah I just read issue #73 and understood the intention better. Right, this is done in SegFiller...

I wrote it there, but the purpose is because this operation is considered as a part of channeling our segmentation label definition to an outside software (i.e. caffe for instance). So that's why it's not a module. We can change if we want to, though!