Allowing setting user status

Summary:
I will use it for highlighting users which are not currently available.

Maybe I will also use it in the nagging tool.

I don't plan creating a UI for it as API is currently enough for us.
Maybe I will visualize it at /calendar/ later.

I plan creating `user.deletestatus` method when this one will be done.

Test Plan:
`storage upgrade`
Call Conduit `user.addstatus`.
Verify DB.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Koolvin

Differential Revision: https://secure.phabricator.com/D2382

resources/sql/patches/userstatus.sql

@@ -0,0 +1,11 @@
+CREATE TABLE {$NAMESPACE}_user.user_status (
+  `id` int unsigned NOT NULL AUTO_INCREMENT,
+  `userPHID` varchar(64) NOT NULL,
+  `dateFrom` int unsigned NOT NULL,
+  `dateTo` int unsigned NOT NULL,
+  `status` tinyint unsigned NOT NULL,
+  `dateCreated` int unsigned NOT NULL,
+  `dateModified` int unsigned NOT NULL,
+  PRIMARY KEY (`id`),
+  INDEX `userPHID_dateFrom` (`userPHID`, `dateTo`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8;