Eliminate copying checked out code to final install directory

[weaverba137]

Historically as part of the desiInstall script, we copied the contents of the working/build directory to the final install directory, in addition to actually installing the code (python setup.py install / make install) in the same directory.

This isn't really necessary anymore, since we've moved necessary package data inside the Python packages themselves, so data gets installed along with the Python package. However, a few packages, particularly desimodel, still need extra data that is downloaded to the build directory, then copied into place.

This issue will track any additional packages that need special data install handling, and the eventual removal of the code. Other issues will track the modification of the data scripts to install directly to the install directory.

[weaverba137]

I looked through every package on https://github.com/desihub, and only desimodel has the script that is automatically invoked by desiInstall.

[weaverba137]

The other reason this capability exists is to support trunk/master/branch installs. Maybe those should be done by hand from now on, especially if we don't change desiconda versions very often.

[weaverba137]

Oops, didn't mean to close.