Touch up documentation strings for DigitalOcean.

This will fix a few of the documentation strings in the DigitalOcean module. I were initially just to fix `Numeric, this is the id of the region you would like your server` being cut off at the end, but added a few more things:
* Consistent spelling of "DigitalOcean".
* Add some periods to those sentences missing them.
* Tiny corrections in wording.
See the change set itself for details.