Isolate the internal SQLite plugin into a library

[theopolis]

There is a bug in how osquery is built as an SDK. The SQLiteSQLPlugin should not be included in static libraries that extensions and whatnot build. In rare cases this plugin and the external SQLlite plugin will "compete". If this plugin is used in an extension then tables that the extension does not know about will be incorrectly labeled as "not found".

This is a hard-to-exercise scenario. A more complete fix would be to refactor how the plugin is selected and force a different name for the external SQL mode.