Summary:
This diff fixes several issues around loading plugin, such as:
* make suresource maps work in the flipper-server production build
* make sure default plugins are no symlinked, which wouldn't work anywhere else but on the the system where it was build
* support release channel param for flipper-server
Bundled flipper-server is now 42MB (with icons (see later diffs) and plugins
```
ll flipper-server-v0.0.0.tgz
-rw-r--r-- 1 mweststrate staff 42M 23 Dec 15:29 flipper-server-v0.0.0.tgz
```
Reviewed By: nikoant
Differential Revision: D33294677
fbshipit-source-id: 63538dc8127f883fee6a3608673ad11ce239b350
