make it easier to release twilio numbers used in local dev

Value

• we make a lot of numbers for local dev that sit around costing us $1/mo even though we might wipe them and stop using them
• it would be nice to tag these as used in dev so we could sweep through and manually delete them ocassionally

Behavior

GIVEN a dev with team-friendo twilio credentials

• WHEN the dev creates a new twilio number for local dev via boost create-number
• THEN that number's "friendly name" will include the term "DEV" (so that a maintainer can search for that term and delete it later -- or better, we could automate that!

Implementation

• in registrar/phoneNumber/purchase#create, read process.env.NODE_ENV and include that in the string passed as the friendlyName param