Add version number to picotool output

[jtraister]

Please add a bi_program_version_string() call with the version number. Right now I have to rely on build date to determine the difference between binaries, but that's not great.

[lurch]

I guess this sort of relates to #113 ?

[jtraister]

I think so, just more info available about the binary.

[fduxiao]

I'm not sure where to get the version string, but I wrote this adding the git tag as version. If HEAD is tagged, then the tag is used for version; otherwise, git commit hash is used. Is this reasonable?

What else is needed? I can add all these to binary information and make a pull request then.