Add function setladj

[oschulz]

@devmotion, this PR mirrors InverseFunctions.setinverse.

With this, we can do stuff like

computation_on_gpu ∘ setladj(setinverse(CuArray, Array), Returns(0)) ∘ computation_on_cpu

I have several used cases that would profit from such "on-the-fly" adding of LADJ-computation (intermediate steps in transforming flows, etc). It's also very handy for demos and tutorials.

This PR also adds with_logabsdet_jacobian support for InverseFunctions.FunctionWithInverse.

CC @cscherrer

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (bdcf78c) 100.00% compared to head (5c58988) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##            master       #22   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         5    +2     
  Lines           61        82   +21     
=========================================
+ Hits            61        82   +21     

Impacted Files	Coverage Δ
src/ChangesOfVariables.jl	100.00% <ø> (ø)
ext/ChangesOfVariablesInverseFunctionsExt.jl	100.00% <100.00%> (ø)
src/setladj.jl	100.00% <100.00%> (ø)

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[devmotion]

LGTM, just some minor comments.

[oschulz]

Thanks for the doc fixes @devmotion !

[oschulz]

I think we're good now.