Support SSL on backend/ability to disable ssl verification

[jensendw]

When running the proxy against an SSL backend I was receiving errors as follows:

[Mon Aug 04 00:03:26 2014] [error] proxy: HTTPS: failed to enable ssl support for [::1]:9443 (localhost)
[Mon Aug 04 00:03:31 2014] [error] [client ::1] SSL Proxy requested for xxx but not enabled [Hint: SSLProxyEngine]

This led to adding the SSLProxyEngine on to the configuration, from my testing this has no bearing if the backend is http

My backend uses a self signed SSL certificate which resulted in the following log messages when running with SSLProxyEngine configured

[Tue Sep 10 18:22:52.959291 2013] [proxy:error] [pid 19531] (502)Unknown error 502: [client 173.xx.xx.xx:9558] AH01084: pass request body failed to 184.xx.xx.xx:2096 (184.xx.xx.xx), referer: https://domain.com:2096

I added the DISABLE_SSL_VERIFY toggle which effectively disables SSL certificate verification against the backend.