Summary:
This function generalizes the normaliseBytestringPackage and other similar
one-off functions into normalise_version() with takes a package name to
normalize against.  This JUST manages package versions; we also could use
a normalize for keys.

In the process, I modified all the normalization functions to be accumulative;
I don't think this makes a difference for current test cases but I think it
makes things nicer.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Reviewers: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D725