Add option to create indexes post-installation

The sphinxsearch daemon will fail after installation because the sphinx
indexer will not have run yet. With "init_index" set to true, the module
will install the package, install the configuration file, run the indexer,
then finally attempt to start the service.

Subsequent runs should not invoke the indexer- Only the initial install.
The indexer should be run at a user-controlled interval (via cron, for
exmaple) and should avoid sphinx::index.