fcm make: extract: detect same diff trees as base

Remove any diff trees in a project that are the same as the base tree.
FCM_CONF_PATH: override site/user conf paths

If FCM_CONF_PATH is defined in the environment, use its value as paths
to site and user configuration files.
Merge pull request #105 from matthewrmshin/env-fcm-conf-path

FCM_CONF_PATH: override site/user conf paths
Merge pull request #103 from matthewrmshin/fcm-make-extract-location-filter

fcm make: extract: detect same diff trees as base
Update CHANGES.md
Document: more prerequisites for admin commands
Doc: installation: checked error with tidy
Merge pull request #107 from matthewrmshin/doc-install-admin

Document: more prerequisites for admin commands