base.install: Using package_type & package_tool

To simplify the distribution support, common is now featuring two
functions:
- package_type() which returns "deb" or "rpm" regarding the targeted
  distro
- package_tool() which returns "apt" or "yum" regarding the targeted
  distro (maybe we'll need yast sometimes)

This make the code easier to read and much more scalable to the kind of
distro we can support