helpers: create package

just created package dir and __init__.py and
moved helpers.py to helpers/misc.py - no other changes.

not functional, some imports need fixing...

src/borg/helpers/__init__.py

@@ -0,0 +1,11 @@
+"""
+This package contains all sorts of small helper / utility functionality,
+that did not fit better elsewhere.
+
+It used to be in borg/helpers.py but was split into the modules in this
+package, which are imported into here for compatibility.
+"""
+
+# misc.py is just the moved/renamed old helpers.py for an easy start.
+# over time, more and more stuff shall be moved from misc to other modules.
+from .misc import *