Require Rewrite again

Summary:
Modify require feature response to return an array of ModuleMetadata instead of toplevel match_route, graphql etc.

The Require feature now returns a list of ModuleMetadata  found when parsing a file. Each module import is distinguished by type ModuletType which is added in this diff. The ModuleType describes the way in which a module is required. The enum values are fairly self-explanatory.

The new ModuleMetadata class contains a list of references where the module was required/imported/etc. These refs contain the call_range and the args_range of the statement.
The args_range represents the range of the import/require/reexport source  ie: const a = require(|'b'|);
The args_range represents the range of the import/require/reexport source. This is in keeping with what what the general require feature expects. ie: const a = require(|'b'|);

In addition, this diff adds reexported modules to the require feature. Reexported modules are referenced in an es6 reexport statement ie `export foo from 'bar'`.

Reviewed By: avp

Differential Revision: D24700998

fbshipit-source-id: f43a128454f0e131987ebf2dd05a914557bc9a49

lib/AST/ESTreeJSONDumper.cpp

@@ -106,7 +106,9 @@ class ESTreeJSONDumper {
     if (locMode_ == LocationDumpMode::Range ||
         locMode_ == LocationDumpMode::LocAndRange) {
       json_.emitKey("range");
+      json_.openArray();
       dumpSMRangeJSON(json_, rng, sm_->findBufferForLoc(rng.Start));
+      json_.closeArray();
     }
   }
 
@@ -457,10 +459,8 @@ void dumpSMRangeJSON(
       rng.Start.getPointer() >= bufStart &&
       rng.End.getPointer() <= buffer->getBufferEnd() &&
       "The range must be within the buffer");
-  json.openArray();
   json.emitValues(
       {rng.Start.getPointer() - bufStart, rng.End.getPointer() - bufStart});
-  json.closeArray();
 }
 
 void dumpESTreeJSON(