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/t01_version/__init__.py

@@ -9,5 +9,6 @@ class VersionTest(BaseTest):
     """
     version should match
     """
+    gold_processor = BaseTest.expand_environ
 
     runCmd = "aptly version"