Added more packages and reorganised the YAML files

This merge restructures the YAML files to make them a little easier to read, and adds some new packages:

• reorganised YAML files into build tools, python tools, and lscsoft packages,
• added some common build tools (compilers, cmake etc);
• added python tools (linters)

EDIT: the compilers metapackage is now available on conda-forge, so I have added that.