This puts config in its relevant location and moves functions around
loading config files into the main package.
As a side effect of removing cyclic imports for the API config, the
context library is no longer used.
This removes the `types` package instead moving the contents to the
top-level clair package.
This change also renames the `Priority` type to `Severity` in order to
reduce confusion.
This change also removes the IsValid method and replaces it with a safe
constructor to avoid the creation of invalid values.
Many docstrings were tweaked in the making of this commit.
There is apparently no reason to ignore empty results - it was probably the case in the past (`null` value).
["", "v"] should be considered invalid by toValue() because it represents two values.
["", "v"] should be returned as it by toValues(), not trimming "".
Tests passes, it will hopefully not cause any issue in prod.
Clair will now use a YAML configuration file instead of command line
arguments as the number of parameters grows.
Also, Clair now exposes a Boot() func that allows everyone to easily
create their own project and load dynamically their own fetchers/updaters.
