[WIP] Report service version via "--version" flag

Now all the services report version when ran with --version flag.

Note: Version string in `st2common/st2common/__init__.py` file needs to be manually updated. I was thinking that we could and probably also should use this is an authoritative file for determining StackStorm version (during build process, in the docs, etc.).
This is kinda nasty, but `oslo.config` communicates version and some other things via logging module which means that before this change, all the messages which were logged by oslo before and during config parsing were quietly swallowed.