Bug fixes:
- Fixed double translation issue for error message in _luceneapi_drush_index_wipe()
- Re-added Drush command "luceneapi cache clear". Accidentally removed command in D5 version.
Minor fixes:
- Addressed a few minor coding style issues.
- Added luceneapi_throw_error() call when returned cached result set is not valid
- Fixed double translation issue in luceneapi_variable_get() and luceneapi_setting_get(). The error messages should only get thrown in development environments.