Move devices to server folder

Summary:
This is the first of many diffs that extracts the connection, device, client detection out of the flipper core, to create a reusable flipper-server library that can be used in e.g. flipper-dump.

To keep diffs a little smaller, the current connection logic is first moved to the `server/` directory, and decoupled manually from the rest of the core, before moving it over to a separate package.

This first diffs moves the `comms/`, `devices/` and certificate utilities to the `server` directory.

Further untangling will follow in next diffs

Reviewed By: timur-valiev

Differential Revision: D30246551

fbshipit-source-id: c84259bfb1239119b3267a51b015e30c3c080866

desktop/app/src/dispatcher/reactNative.tsx

@@ -8,7 +8,7 @@
  */
 
 import {remote} from 'electron';
-import MetroDevice from '../devices/MetroDevice';
+import MetroDevice from '../server/devices/MetroDevice';
 import {Store} from '../reducers';
 
 type ShortcutEventCommand =