The URL Scheme the HTTP Message is incorrect when using proxy

This only impacts CBL-C which is using LiteCore's BuiltInWebSocket. Currently when using proxy, the scheme or the target URL in the start line of the HTTP message is is ws or wss, which is not correct (See the example below). The scheme should be http or https.

Note: I have tested the issue with the mitmproxy.

Example 

Incorrect (Current)

GET ws://192.168.86.203:4984/db/_blipsync HTTP/1.1 

Correct

GET http://192.168.86.203:4984/db/_blipsync HTTP/1.1