[INTERNAL] abstracted IPath creation

The marshalling/unmarshalling is now done in a dedicated factory which
must be present at runtime in the context.

Change-Id: Ic511d2f8ad70561fa2204fa52cf3ed6229051234
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1423
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>