At its start, SimpleConfigurator bundle does the followings.
1. A value will be gotten by @{link BundleContext#getProperty(key)} with
SimpleConfiguratorConstants.PROP_KEY_CONFIGURL as a key.
The value will be used for the referal URL. Under the url, there must be a simple
bundles list file to be installed with thier start level and flag of marked as started.
2. If the value is null, do nothing any more.
3. Otherwise, retrieve the bundles list from the url and install,
set start level of and start bundles, as specified.
4. A value will be gotten by @{link BundleContext#getProperty(key)} with
SimpleConfiguratorConstants.PROP_KEY_EXCLUSIVE_INSTALLATION as a key.
5. If it equals "false", it will do exclusive installation, which means that
the bundles will not be listed in the specified url but installed at the time
of the method call except SystemBundle will be uninstalled.
Otherwise, no uninstallation will not be done.