Support customising the LightBlue data directory

[ColinScott]

Support using an alternate path for the LightBlue data directory.

[Drewan]

The default data directory is local app data but you can change it before the LightBlue context is created.

StandaloneEnvironment.LightBlueDataDirectory = @"c:\ProgramData\LightBlue";

I think all that would be required is to add an overload to LightBlueConfiguration.SetAsLightBlue() that takes a file path to be used as the data directory.