engine: Improving export of xmls

The following patch is one of the first step which is done in order to improve our
xml read/write infrastructure.
The change contains:
1. During export of xml no need to create a temp file and after that load it, the following code was removed.
2. Clean up of appropriate files
3. removing un needed classes
Main benefits, perfromance should be improved on every export xml operation (removed i/o), code should become
more clean

Change-Id: If8206580740be92cac7ffdbdc1c2f53ac0021d2e
Signed-off-by: Michael Kublin <mkublin@redhat.com>