Versionalize client for installation with `go install`

[matheusd]

This would make it easier to install and use the dcrtime client for us developers. This would (roughly) require:

• Add some versioning info, available from -version
• Embed the sample-dcrtime.conf file (instead of relying on it to be on the path)
• Tag module versions for release
• Add instructions to repo on how to install (go install ...)
• Add instructions to timestamply on how to install

[decredclub]

This is a great addition, I was trying to add a language pack and it was inconvenient to install and test it locally!