Make how Solr_Configure uploads config replaceable

Solr_Configure takes the `indexstore.mode` configuration variable to set how
to upload new configuration to the Solr server. However the various modes
were within Solr_Configure and you couldnt add more without altering the module

This changes Solr_Configure to make the configuration upload portion
contained with a seperate class thats selected via `indexstore.mode`
to fix that.
Merge pull request #28 from hafriedlander/api/injectableconfigstores

Make how Solr_Configure uploads config replaceable