[hack] Persistent connection prototype
[hack] Persistent connection prototype

Summary:
- Set up basic "echo" version of persistent connection between client and hh_server using ide command
- Messages from server to client use preamble
- Messages from client to server still use channels since mixing the use of preambles with channels will generate problems
(maybe update all commnication to use preambles later)

Reviewed By: dabek

Differential Revision: D3462415

fbshipit-source-id: e862f6dc4f7d7ff7b515af7951d25534b8e72494

AgentME/flow,jdelStrother/flow,jgrund/flow,jeffmo/flow,claudiopro/flow,mroch/flow,jamesgpearce/flow,ForbesLindesay/flow,jeffmo/flow,nmote/flow,mroch/flow,jamesgpearce/flow,jgrund/flow,samwgoldman/flow,jdelStrother/flow,popham/flow,gabro/flow,facebook/flow,fletcherw/flow,ForbesLindesay/flow,jgrund/flow,AprilArcus/flow,ylu1317/flow,jeffmo/flow,AgentME/flow,jgrund/flow,popham/flow,JonathanUsername/flow,AprilArcus/flow,jgrund/flow,mroch/flow,samwgoldman/flow,AgentME/flow,fletcherw/flow,TiddoLangerak/flow,gabro/flow,popham/flow,popham/flow,samwgoldman/flow,facebook/flow,TiddoLangerak/flow,nmote/flow,chenglou/flow,facebook/flow,jamesgpearce/flow,jdelStrother/flow,nmote/flow,TiddoLangerak/flow,chenglou/flow,mroch/flow,samwgoldman/flow,gabelevi/flow,mroch/flow,ylu1317/flow,MichaelDeBoey/flow,TiddoLangerak/flow,gabro/flow,gabro/flow,gabelevi/flow,ylu1317/flow,jeffmo/flow,jamesgpearce/flow,popham/flow,popham/flow,AprilArcus/flow,gabelevi/flow,gabelevi/flow,claudiopro/flow,JonathanUsername/flow,AprilArcus/flow,samwgoldman/flow,claudiopro/flow,JonathanUsername/flow,mroch/flow,claudiopro/flow,jdelStrother/flow,samwgoldman/flow,jdelStrother/flow,facebook/flow,jeffmo/flow,mroch/flow,chenglou/flow,MichaelDeBoey/flow,AgentME/flow,ForbesLindesay/flow,gabelevi/flow,MichaelDeBoey/flow,facebook/flow,samwgoldman/flow,jgrund/flow,nmote/flow,jeffmo/flow,gabelevi/flow,ForbesLindesay/flow,gabro/flow,TiddoLangerak/flow,jdelStrother/flow,AprilArcus/flow,chenglou/flow,fletcherw/flow,popham/flow,JonathanUsername/flow,AprilArcus/flow,facebook/flow,gabro/flow,ylu1317/flow,JonathanUsername/flow,JonathanUsername/flow,chenglou/flow,fletcherw/flow,nmote/flow,ForbesLindesay/flow,ForbesLindesay/flow,JonathanUsername/flow,chenglou/flow,fletcherw/flow,jamesgpearce/flow,gabelevi/flow,ylu1317/flow,AgentME/flow,jamesgpearce/flow,nmote/flow,MichaelDeBoey/flow,claudiopro/flow,fletcherw/flow,nmote/flow,jamesgpearce/flow,facebook/flow,MichaelDeBoey/flow