Also put all the hook additions in a single place, instead of in each
special function. Both the advantages to this method are:
- Being able to see in a second where flycheck is enabled.
- If all minor modes are added separately it's easy to see exactly
which are enabled for a specific mode, just by looking at its hook
variable.
The new uninstall functionality tries to remove any "orphan" files.
Files that were installed during the last install, but will not be
installed this time (because of removal, not necessity).
