Bump version to 0.0.20

Overview of changes:

 *  Fixed non-existent cache on first run breaking locking

mkit.ini

 [project]
-    version     = 0.0.19
+    version     = 0.0.20
     name        = imapdomo
     pkgname     = imapdomo
     maintainer  = Alois Mahdal <netvor+imapdomo@vornet.cz>