change directory structure

[pca006132]

Closes #701. Closes #917.

1. Moved every (public) headers into the manifold directory.
2. Changed public.h to common.h and par.h to parallel.h.
3. Install parallel.h and iters.h

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.40%. Comparing base (d437097) to head (5e5bbcf).
Report is 88 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #918      +/-   ##
==========================================
- Coverage   91.84%   88.40%   -3.44%     
==========================================
  Files          37       62      +25     
  Lines        4976     8660    +3684     
  Branches        0     1059    +1059     
==========================================
+ Hits         4570     7656    +3086     
- Misses        406     1004     +598     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[hzeller]

Nice! LGTM.

[elalish]

Sounds good. My only thoughts, and I'm not at all sure these are good, is would it be nice if all the public manifold headers were in the same directory? Or is that confusing? And likewise, would it be helpful to separate the public headers like common.h from the internal headers like vec.h into different directories?

[pca006132]

Separating the headers sounds good, but I am not sure how to do this with our current module organization. Having 2 header directories in the same module seems a bit too cluttered to me. Anyway, that will not be public facing changes, so it should be fine to do it later I guess.

[hzeller]

maybe there could be an internal/ subdirectory. But also agree, that can be refined later.