Start refactoring code toward pluggable installers
Start refactoring code toward pluggable installers

Still needs to be extracted entirely, but it provides the start.

mikecroucher/conda-env,conda/conda-env,phobson/conda-env,nicoddemus/conda-env,isaac-kit/conda-env,phobson/conda-env,dan-blanchard/conda-env,isaac-kit/conda-env,ESSS/conda-env,asmeurer/conda-env,dan-blanchard/conda-env,nicoddemus/conda-env,mikecroucher/conda-env,conda/conda-env,ESSS/conda-env,asmeurer/conda-env