Indirect File click types

[ttung]

Add the ability to reference an imagestack or a codebook through a set of conversion recipes. Each conversion recipe can read the input given on the CLI and make an attempt to convert it to the desired type.

For instance, a primary image can be referred to by the json describing the slicedimage set, or @experiment.json[my_fov_name][primary].

[ttung]

Here's an example of how this works:
931666e

[codecov-io]

Codecov Report

Merging #1124 into master will decrease coverage by 1.79%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master    #1124     +/-   ##
=========================================
- Coverage   90.41%   88.62%   -1.8%     
=========================================
  Files         125      130      +5     
  Lines        4550     4642     +92     
=========================================
  Hits         4114     4114             
- Misses        436      528     +92

Impacted Files	Coverage Δ
starfish/util/indirectfile/_base.py	0% <0%> (ø)
starfish/util/click/indirectparams.py	0% <0%> (ø)
starfish/util/indirectfile/_codebook.py	0% <0%> (ø)
starfish/util/indirectfile/__init__.py	0% <0%> (ø)
starfish/util/indirectfile/_imagestack.py	0% <0%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 16bb36e...8c8c39a. Read the comment docs.

[ttung]

I refactored this a bit to separate out the conversion logic from the click logic. Rationale: I want to be able to use this in the pipeline recipes. However, the recipes will not be able to use the click params, because at the time we generate the click.command calls, we do not know the types! Only when we parse the recipe do we know what type they will be.

I will wait for this to be green before landing, but if you want to do a post-merge review, please do! :)