Add support for rsync --exclude to speed up deployment

[deardaniel]

This simply adds a copy_exclude configuration option that is converted to rsync --exclude parameters.

Similar in implementation to remote_cache.

[reagent]

Added in 4c19355. Two things to note:

• I only use --exclude when syncing the local cache to the remote server, syncing to the release directory doesn't need this flag since the source does not contain the excluded files.
• I needed to change the default --delete flag to --delete-excluded so that the excluded files are removed from the remote directory (in case they were there previously). --delete-excluded implies --delete, so it's a drop-in replacement.

Let me know if this addresses your original issue.