Specifying image/VM version

[cdlm]

Fari should have a way to download various images/VM versions (e.g. 6.0, 6.1, 7.0… and stable/latest, 32/64-bit). Possibilities to specify version info:

• fari build arguments
• specified in load.st files (but what syntax… magic comment?)
• separate config FariFile
• environment variables

[cdlm]

PharoLauncher already has code for this, so this might have to wait until the unavoidable rewrite in Smalltalk 😉