Clean up module dependencies.

- LoggerFactory does not depend on SIP
- Constants depends only on SIP.name and SIP.version
- Exceptions does not depend on SIP
- Timers does not depend on SIP
- Transport depends on window
- SIP.MediaHandler depends on EventEmitter, not SIP
- WebRTC depends on Utils, not SIP
- Hacks depends on window, not SIP
- DigestAuthentication depends on Utils, not SIP