* The Install() and Update() versions that take a const char* array
now check whether a string looks like a path to a local package file.
If so, they use that file instead of interpreting the string as a
search string.
* Extend the repository hierarchy. There's now a LocalRepository base
class from which InstalledRepository and the new MiscLocalRepository
derive. The latter is instantiated once and collects all package files
specified by path.