Timer for tasks, servers autoupdating and other.

Added Timer - great package which will make periodic tasks to work.
Timer exposes "taskDone" event, which can be triggered when
task ends it's execution.

Added first periodic task - servers information updating. By
default it will execute every 10 minutes. Configurable thru
options.

Added new options pane: Servers updating. It controls all aspects
of servers updating thing. Master server address, servers
autoupdating checkbox and autoupdate timeout values are exposed
for now.

We're now on on 0.2.0-devel :).

Fixes #29.

requester/pooler.go

@@ -68,9 +68,12 @@ func (p *Pooler) PingServers(servers_type string) {
             continue
         }
         for {
+            p.cur_requests_mutex.Lock()
             if cur_requests == p.maxrequests {
+                p.cur_requests_mutex.Unlock()
                 time.Sleep(time.Second * 1)
             } else {
+                p.cur_requests_mutex.Unlock()
                 break
             }
         }