Use `__all__` when loading modules(if provided).

* When loading the module's functions, if the module provides `__all__`, that's what's iterated.
* If a function provided in `__all__` starts with `_` it's not skipped because the module explicitly provided it.
* Minor formatting in the logging messages.
Remove forgotten `)`. Minor PEP8.
To avoid any future confusion, we'll use `__load__` instead of `__all__`.
Merge branch 'develop' of github.com:saltstack/salt into hotfix/use-module-__all__-in-loader
Besides loading module functions from `__load__` we also log that information.

This will allow us to debug any bug reports stating that the function X is not loading(because they did not add it to an existing `__load__`).
Merge pull request #3771 from s0undt3ch/hotfix/use-module-__all__-in-loader

Use `__all__` when loading modules(if provided).