Add subprojects to a main project.

Summary:
Quite basic subproject attachment.

Test Plan:
Go to some proj
ect and add another as a subproject.
Play around the ui.

Reviewers:	epr
iestley
CC:

resources/sql/patches/064.subporjects.sql

@@ -0,0 +1,11 @@
+ALTER TABLE phabricator_project.project
+  ADD subprojectPHIDs longblob NOT NULL;
+UPDATE phabricator_project.project
+  SET subprojectPHIDs = '[]';
+  
+CREATE TABLE phabricator_project.project_subproject (
+  projectPHID varchar(64) BINARY NOT NULL,
+  subprojectPHID varchar(64) BINARY NOT NULL,
+  PRIMARY KEY (subprojectPHID, projectPHID),
+  UNIQUE KEY (projectPHID, subprojectPHID)
+);