Convert to int in fact_from_dbus

Created by: GeraldJansen

In the creation of a Fact() coming from dbus, explicitly convert dbus integer types to standard ints. This is an alternative work-around for #477 (closed). It should increase uniformity and help guard against other possible type issues for facts coming from dbus compared to facts created directly by hamster.

I have tested this with python 3.7.3 and dbus 1.2.8 by running tests/stuff_tests.py and by creating tasks with hamster-cli and editing them with the GUI.