Implement replacement for ERFResourceRepository to fix patcher.

OEIShared.IO.ERFResourceRepository opens ERF files but does not
allow share delete, so the content patcher cannot replace a hak
file while the server is running (by renaming the old one away).

Integrate a (read only) compatible ALFAERFResourceRepository that
opens the ERF with share delete, and switch over to using it.

Note that ALFAERFResourceRepository does not support creating or
copying resource entries (i.e., no editing of the ERF allowed).
This functionality is not required by the ACR for HAKs being read
via the ACR resource system.