Automatic versioning for aptly

New version format:

* for releases, `x.y.z` (follows tag without leading `v`)
* for nightly builds, `x.y.z+N+hash` (previous version, not the upcoming one)

This means that each nightly build `aptly` would report
correct version now.

Version is now complied into the aptly binary, system tests
automatically check for current version, no need to update them
anymore.

system/t12_api/systemd_handover.py

@@ -1,10 +1,11 @@
 import requests_unixsocket
-import time
 import urllib
+import os
 import os.path
 
 from lib import BaseTest
 
+
 class SystemdAPIHandoverTest(BaseTest):
     aptly_server = None
     socket_path = "/tmp/_aptly_systemdapihandovertest.sock"
@@ -37,9 +38,9 @@ class SystemdAPIHandoverTest(BaseTest):
     Verify we can listen on a unix domain socket.
     """
     def check(self):
-        if self.aptly_server == None:
+        if self.aptly_server is None:
             print("Skipping test as we failed to setup a listener.")
             return
         session = requests_unixsocket.Session()
         r = session.get('http+unix://%s/api/version' % urllib.quote(self.socket_path, safe=''))
-        self.check_equal(r.json(), {'Version': '0.9.8~dev'})
+        self.check_equal(r.json(), {'Version': os.environ['APTLY_VERSION']})