Merge branch 'tickets/3.x/14136' of https://github.com/domcleal/puppet into 3.0rc

(#14136) Emit debug/warnings when Augeas provider fails to load files
Originally submitted as #733 against master, re-targeting to 3.x now the
branch exists.

The messages and information from /augeas//error are now printed to
debug when the provider opens Augeas, allowing file parse errors to be
found.

The provider can also restrict the files that are loaded (from the
default of everything). In these cases, the provider now emits a warning
and then prints all the detailed information to debug. Since a few parse
errors are common, no warning is given when these optimisations aren't
in use.

Conflicts:
CHANGELOG
lib/puppet/provider/augeas/augeas.rb