Add support for controlling the openoffice server process from XWiki UI

Currently the openoffice server process needs to be manually started external to XE. With the release of jodconverter 3.0 however it's possible to control (start/stop) the oo server process within officeimporter itself. This feature should include:

1. A component that controls the oo server process (OpenOfficeServermanager).
2. A velocity bridge that allows velocity scripts to manipulate / query the OpenOfficeServerManager.
3. Configuration options in WEB-INF/xwiki.properties file that allow administrators to configure the oo server process.
4. An admin UI that allows systen administrators to control / view status of the oo server process.