Language selection guidelines

https://wikia-inc.atlassian.net/browse/AR-18

The question of which languages do we support and what is the criteria for evaluating new languages has come up several times. This is an attempt to create a guideline that covers these topics and guide the decision making process.

/cc @pchojnacki @nmonterroso 
@drsnyder 
By 'this group' I meant the 'legacy, not (yet) supported languages group'. Misunderstandings do happen :)

I understand Scala is not to be chosen for service development without prior analysis according to the questions given in the guideline.
However, this is also the reason I asked - what is the rationale behind a decision to move Scala to 'legacy' group - or  to be even more precise: what is the rationale behind moving any of the three languages into the 'legacy' group?

I consider understanding the criteria we'll all be applying in the technology selection domain to be crucial and that's why I believe we need to be explicit about it.

Thanks in advance for the info!