Cloud deprecations for Helium

There were several things in salt-cloud that have been marked for deprecation. I have made the following changes:
- Added all deprecation changes to release notes
- Removed `vm_config` and -vm_config_path` arguments from `cloud_config` function in `salt/config.py`
- Removed the `libcloud_version` function from `salt/cloud/libcloudfuncs.py`
- Removed the `CloudConfigMixIn` class from `salt/utils/parsers.py`
- Removed unit tests that were testing against the use of deprecated functions (no longer applicable)

@s0undt3ch and @techhat - can you please review these changes? (carefully!) :)