KeymanWeb has long had `keyman.build` and `keyman.version`. Neither of
these properties expose the full version string, and consumers are
forced to manipulate them to get a partial version string.
This change deprecates both these properties, and introduces a new
`keyman.versionInfo` property, which returns an object with all the
version information, most importantly `full`.
Update documentation and add a unit test for this, following the unit
test pattern established throughout Keyman of a unit test filename
matching the implementation class. The `KeymanEngineBase` class is a
little difficult to instantiate so this unit test module currently has
a minimal instantiation which provides enough to fulfill the one
included test.
Test-bot: skip
