Fix logrotation rules

* explicitly specify the dirs that are getting rotated
* app log rules are now moved to logrotate.ejs
* we keep task logs for a week

Some testing notes:
* touch -d "10 days ago" foo
* logrotate /etc/logrotate.conf -v to test rotation. there is a state
file created in /var/lib/logrotate/status. If we have a 'daily' rule,
it will get processed only after a log line in status exists and it's atleast
1 day old timestamp.

https://github.com/logrotate/logrotate/blob/master/logrotate.c is quite
readable

src/apptask.js

@@ -232,7 +232,7 @@ function addLogrotateConfig(app, callback) {
         if (!runVolume) return callback(new Error('App does not have /run mounted'));
 
         // logrotate configs can have arbitrary commands, so the config files must be owned by root
-        var logrotateConf = ejs.render(LOGROTATE_CONFIG_EJS, { volumePath: runVolume.Source });
+        var logrotateConf = ejs.render(LOGROTATE_CONFIG_EJS, { volumePath: runVolume.Source, appId: app.id });
         var tmpFilePath = path.join(os.tmpdir(), app.id + '.logrotate');
         fs.writeFile(tmpFilePath, logrotateConf, function (error) {
             if (error) return callback(error);