installation: Apache configuration updates
- Adds config variable to set the number of Apache WSGI daemon processes in generated configuration files.
- Removes etag generation.
- Fixes an issue where WSGIPythonHome would not be set correctly due to VIRTUAL_ENV environment variable not being available when running inveniomanage with sudo.
Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>