RF: Add resamping.apply to top module imports

[mgxd]

This PR is for convenience after #195

[effigies]

I've been thinking that maybe apply() isn't a great name. nitransforms.apply() is at least clear what kind of thing is being applied, but maybe we really want nitransforms.resample() to be explicit about how we're applying a transform.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.76%. Comparing base (e7757e2) to head (269bc7f).
Report is 23 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #227      +/-   ##
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+ Coverage   94.65%   94.76%   +0.11%     
==========================================
  Files          15       15              
  Lines        1758     1759       +1     
  Branches      329      225     -104     
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+ Hits         1664     1667       +3     
+ Misses         77       76       -1     
+ Partials       17       16       -1     

Flag	Coverage Δ
unittests	94.65% <100.00%> (+<0.01%)	⬆️

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[mgxd]

Yeah technically true - I wouldn't be opposed. Just quickly started aggregating a list of what other tools are calling this, seems it goes either way.

Other tools

ANTs: ApplyTransforms
FSL: ApplyXFM
Workbench: -{volume, surface, ...}-resample
FreeSurfer: vol2vol

I do think it should be consistently named throughout (no aliasing at the top level), so if we decided to go forward with that let's do it in a separate API breaking PR

[effigies]

Also: skimage.warp