Avoid hard-coding the version number in the Silver driver

[krame505]

We currently hard-code the version number in the Silver driver, which is a bit suboptimal as it quickly can get out of date, and it would be more useful to know what the latest commit was anyway.

One fix would be to have self-compile and deep-rebuild call a script that updates a file in the driver containing only a global with a version string, computed from the output of git describe --tags. This gives much more useful version info of the form v0.4.4 if the most recent commit has a tag, or else something like v0.4.4-1772-g99dcddc58: the most recent tag, the number of commits since that tag, and an appended hash such that one can query git show v0.4.4-1772-g99dcddc58 to view the latest commit.