UC-258 - emergency dialing feature

In sipXconfig:
- ERL table with possibility to add locations and ELINs
- Users and phones linked to ERLs
REST API to:
- save/update ERLs
- link users to ERL

SIP-213: New proxy plugin that rewrites from uri for emergency calling if an e911 line identifier is configured for the caller.
XXX-XXXXXXXXXXXXXXX
moved
XXX-XXX
XX-XXX