apt_repository: fix update cache after state=changed. Closes GH-4136
Remove duplicate docs in digital ocean module.

The EXAMPLES block here has two copies of the same docs,
one nicely formatted, the other less so.

It looks like a pass was made to clean up the docs but the old
cruftier ones were never removed.
Remove trailing whitespace in digital ocean module.
Merge pull request #4148 from ralphbean/digital_ocean_cleanup

Cosmetic - Digital ocean cleanup
apt_repository: added option update_cache.

The default behavior is to update_cache if changed.

If you add more then one repo, you may not want to update cache for every repo separately.
So you can now disable update_cache with this new option e.g. update_cache=no

Updating cache can also be handled using the apt module.
Fixing up some search/replace errors regarding user/remote_user
Merge branch 'fix/apt_repository_update_cache' of https://github.com/resmo/ansible into resmo-fix/apt_repository_update_cache