Remove unnecessary SUBDOMAIN_INSTALL constant

Core treats everything as subdirectories by default unless this
is set. No need to force it.
Remove P2 plugins from repository in favor of package

We'll be maintaining a package repo that contains all of these so
that they can easily be published to multiple locations.
Revert "Remove P2 plugins from repository in favor of package"

This reverts commit ca24008fb23808d69fa14ea5c4173ed099ebe32f.
Add WP By Email plugin to repository
Add a list of files to exclude during rsync
Merge pull request #8 from washingtonstateuniversity/work0310

[PR] Better deployment prep