Fixes #20: add an extra file for CouchDB to put uuid into

CouchDB will put the `uuid` into the 'last file in the configuration
chain' (see: https://issues.apache.org/jira/browse/COUCHDB-2064). Added
a file that will be last lexicographically (with name in upper case), so
the file managed by Chef won't be touched on every restart.
Personally, I uses the following setup:
- `default.ini` remains as is as CouchDB ships
- `local.ini` contains all my local settings which I'd like to see by default everywhere
- `local.d/${INSTANCE}.ini` - host specific config which includes uuid, admins, cookie secret and, since it occurs the last one in chain, every other options which was set via `PUT /_config`

So, in your setup, on first install Chief generates `local.ini` according your requirements and touches `local.d/${HOSTNAME}.ini`. On first start CouchDB writes uuid, secret and any other options to own file. On update with Chief you're free to regenerate `local.ini` - all local server changes are preserved, nothing else is need to do. The `${INSTANCE}` variable itself points on instance name - for most cases it's just a host name, but if you serve multiple CouchDB instances on the same server it also serve to help you to specify correct config file for each instance. The `${INSTANCE}.ini` naming itself also helpful for backups to guess from where file comes from and where it should be landed, especially if naming policy is pretty clear and transparent.

In the result we keep CouchDB default configuration + provides our own custom one which we would like to see by the default + each instance maintains own configuration without clashes with neighbourhoods.