Report semantic version of OpenBEL API

[abargnesi]

The OpenBEL API should report the API version. The API is not stable yet so this should reflect the 0.x.x series. Until 1.x.x we should expect breaking changes to be possible as it evolves.

The API version uses Semantic Versioning so it's reasonable to report both a version string and granular structure. Something like:

With Accept: text/plain or ?format=text

0.5.0

With Accept: application/json or ?format=json

{
    "version": {
        "string": "0.5.0",
        "major": "0",
        "minor": "5",
        "patch": "0"
    }
}

[abargnesi]

Added GET /api/version that reports the semantic version of the OpenBEL API. It supports JSON or TEXT depending on Accept header or ?format=json|text query parameter.

Added -v and --version options to openbel-api and openbel-config commands.