Make map/reduce APIs more intuitive

[ttung]

Right now, specifying a FunctionSource along with function parameters makes for a confusing function call.

For instance, Map('divide', 2, module=FunctionSource.np) means the FunctionSource comes last, which is not intuitive.

This adds the ability for FunctionSources to be called and return a Bundle that includes both the package name and the function name. The call above would then become: Map(FunctionSource.np('divide'), 2).

Backwards compatibility with the prior API is maintained, but a warning is generated.

If the top-level package is provided twice, it is treated as an error.

Test plan: added test cases to cover the new approach, the old approach that should generate the warning, and the ugly combination that should fail.

[codecov-io]

Codecov Report

Merging #1686 into master will decrease coverage by 0.02%.
The diff coverage is 89.7%.

@@            Coverage Diff             @@
##           master    #1686      +/-   ##
==========================================
- Coverage   89.79%   89.76%   -0.03%     
==========================================
  Files         239      239              
  Lines        8975     9020      +45     
==========================================
+ Hits         8059     8097      +38     
- Misses        916      923       +7

Impacted Files	Coverage Δ
starfish/types.py	100% <ø> (ø)	⬆️
starfish/core/imagestack/imagestack.py	92.04% <ø> (ø)	⬆️
...h/core/spots/FindSpots/test/test_spot_detection.py	100% <100%> (ø)	⬆️
...core/spots/DecodeSpots/test/test_trace_builders.py	100% <100%> (ø)	⬆️
...h/core/spots/FindSpots/test/test_synthetic_data.py	100% <100%> (ø)	⬆️
starfish/core/image/Filter/reduce.py	95% <100%> (+1.45%)	⬆️
starfish/core/types/__init__.py	100% <100%> (ø)	⬆️
starfish/core/types/_functionsource.py	90.62% <100%> (+2.16%)	⬆️
starfish/core/image/Filter/test/test_reduce.py	98.41% <100%> (+0.23%)	⬆️
starfish/core/image/Filter/test/test_map.py	100% <100%> (ø)	⬆️
... and 2 more

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[shanaxel42]

I actually didn't find the old method confusing. Was it breaking anything? I don't have a huge preference if you think this makes more sense but seems like a lot of changes

[ttung]

It gets even more confusing when the function takes kwargs, because it becomes:

Reduce('function_name', function_positonal_arg0, function_positonal_arg1, module=FunctionSource.blahblah, function_kwarg_0=val, function_kwarg_1=val)

[shanaxel42]

It gets even more confusing when the function takes kwargs, because it becomes:

Reduce('function_name', function_positonal_arg0, function_positonal_arg1, module=FunctionSource.blahblah, function_kwarg_0=val, function_kwarg_1=val)

Ahhh ok then I support this.