SkyHTTP

[mrpalide]

Did you run make format && make check? Yes

Fixes #1696

Changes:

• add new app SkyHTTP (known as skyhttp on configs) for running http-proxy behind skysocks proxy.

How to test this PR:

• build
• run skysocks-client
• modify skyhttp args with addr and socks, related to http-proxy address and skysocks address
• test http-proxy on some apps like Mozilla Firefox

[mrpalide]

Closed, due to new PR https://github.com/skycoin/skywire/pull/1728/