remove duplicate strictness enforcement

readFile' is already enforcing strictness.
Clarifying the purpose of ParseC

I had forgotten what it was for, and I don't want this to happen again.
adding missing imports
use the existing shortcut 'display'
a parser for cabal's cache file
read the versions from the actual cache file
symmetry between cabalPath and cachePath
restrict the versionMap to the packages we need
reorganizing the file hierarchy
whitespace.
remove unused imports