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__`.
Re-apply 3055916b5ddcea62885a637c3a26a4e7d75b6107 correcting the copy/paste error. Refs #2563.

We should now provide the configuration filename to load configurations from at the parser's class level.
The calls to `ConfigDirMixIn.get_config_file_path()` still accept a filename, though, if that filename is `None`(the default), it grabs the filename from the class level attribute `_config_filename_`.
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 #3787 from s0undt3ch/issues/2563

Re-apply 3055916b5ddcea62885a637c3a26a4e7d75b6107 correcting the copy/paste error. Refs #2563.
Merge pull request #3771 from s0undt3ch/hotfix/use-module-__all__-in-loader

Use `__all__` when loading modules(if provided).
Fix problem with test=True for bin pkg install

Thought I had fixed this in 4149529 but I was mistaken.
Add more seeding to the qemu functions
Fix soem hicups in the qemu seed
fixing host field syntax for salt.states.mysql_grants
Merge pull request #3791 from christisking/develop

fixing host field syntax for salt.states.mysql_grants
Allow virt.init to seed vm images before starting up
Update README.rst
Merge pull request #3792 from archtaku/issue3731

Fix problem with test=True for binary pkg install
hook seed into virt runner
double verify the nbd connecti
Allow specifying private key files for Git commands that use SSH
Merge pull request #3793 from chideit/git-identity

Allow specifying private key files for Git commands that use SSH