Include network in forest version string.

[lemmih]

Summary of changes
Changes introduced in this pull request:

• Include network (eg. mainnet or devnet) in the version string shown with forest --version.

Reference issue to close (if applicable)

Other information and links

Target network is selected at compile time but the forest executable couldn't show which network had been selected.

[q9f]

I do not disagree with having this as part of the version string as long as this is a compile-time feature.

[connormullett]

👍