DOCUMENT-112: Clarifying DirectoryMatch info

If in a Directory block you set the provider to "directorymatch", then it will use the keyword DirectoryMatch in the apache config file. This was not noted in the readme. Now it is.

I also did a bit of light general copy editing, as is the custom of my people.
The "and it can be a regex for matching providers" sounds awkward in some way. How about something more explicit like "Its value must be a path for the 'directory', 'files', and 'location' providers, or a regex for the 'directorymatch', 'filesmatch', or 'locationmatch' providers."