[multiple proxies] support for multiple proxies and optionally a static redirect

- multiple proxies allows you to proxy say /api -> localhost:8000/api and at the same time, proxy /some-other-api to localhost:8001 for example
- this also tweaks the way proxies are set up in general so that you can proxy to a target without the proxy path or not depending on what you want (e.g. you can do /api -> localhost:8000/api if you want to preserve /api in the target OR you could do /api -> localhost:8000 if you did NOT want to preserve /api in the target)
- finally, this also supports the concept of a static redirect (e.g. instead of /api/* it would be /api and would simply only ever do a redirect for that exact match)

Signed-off-by: danjamin <e051ba3be@gmail.com>