res_aeap: Add basic config skeleton and CLI commands.

Added support for a basic AEAP configuration read from aeap.conf.
Also added 2 CLI commands for showing individual configurations as
well as all of them: aeap show server <id> and aeap show servers.

Only one configuration option is required at the moment, and that one is
server_url. It must be a websocket URL. The other option, codecs, is
optional and will be used over the codecs specified on the endpoint if
provided.

https://wiki.asterisk.org/wiki/pages/viewpage.action?pageId=45482453

Change-Id: I567ac5148c92b98d29d2ad83421b416b75ffdaa3