Draft: pin core conda-analytics packages

Versions of crucial packages in Conda-Analytics are pinned in conda-environment.yml which is used to generate the conda-environment.lock.yml file which we use to be able to EXACTLY reproduce an environment by just installing and downloading the packages needed. This is particularly handy in the context of conda-anlytics where you use conda to provision environments in various places. However, those files just specify what versions should be installed in the new environment to start; Conda happily ignores them in all future transactions. This doesn't just mean that package A will be updated if the user runs conda update A. If the user runs conda install B and B lists A as a dependency, Conda will automatically upgrade A to the latest version (even if B's requirement is already satisfied by the existing version). This has caused some environment problems! case some Conda-Analytics packages are incompatible with the latest versions of Pandas and Numpy causing issues when releasing new version of Wmfdata-Python.

This patch intoduces the pinned file which can be used to pin essential package versions. Pinned specs are included with each conda install, subsequent conda update commands