Report version number accurately for new builds

[chrismear]

Say we release version 3.2.1, and then make a few commits of new development work. Someone running the latest commit still sees the version number reported in-app as '3.2.1', even though this is a newer version.

Could we automatically report a version number like '3.2.1+build.e67f3a' by using the Git commit ID? Then it's clear to a tester (or an adventurous user) that they're not really using version 3.2.1.