Move search settings to configuration app. Closes #177

[pollardld]

This pull request includes significant changes to the handling of search settings within the TEKDB application. The main updates involve removing the SearchSettings model and moving its configuration to the Configuration model, along with several related adjustments across the codebase.

Removal of SearchSettings model:

• TEKDB/TEKDB/admin.py: Removed SearchSettingsAdmin class and unregistered SearchSettings from the admin site. [1] [2]
• TEKDB/TEKDB/migrations/0018_delete_searchsettings.py: Added migration to delete the SearchSettings model.
• TEKDB/TEKDB/models.py: Removed SearchSettings model definition.

Migration of search settings to Configuration model:

• TEKDB/configuration/admin.py: Added min_search_rank and min_search_similarity fields to the ConfigurationAdmin class.
• TEKDB/configuration/migrations/0012_auto_20241025_1313.py: Added migration to include min_search_rank and min_search_similarity fields in the Configuration model.
• TEKDB/configuration/migrations/0013_auto_20241025_1406.py: Updated migration to include choices for min_search_rank and min_search_similarity fields.
• TEKDB/configuration/migrations/0014_auto_20241025_1603.py: Further updated migration to refine choices for min_search_rank and min_search_similarity fields.
• TEKDB/configuration/models.py: Added min_search_rank and min_search_similarity fields with choices to the Configuration model.

Updates to search settings logic:

• TEKDB/TEKDB/context_processors.py: Modified search_settings function to handle new configuration logic and fallback mechanisms.
• TEKDB/TEKDB/models.py: Updated run_keyword_search function to use the new search_settings function.

Configuration changes:

• TEKDB/TEKDB/settings.py: Adjusted MIN_SEARCH_RANK and MIN_SEARCH_SIMILARITY default values and added search_settings context processor. [1] [2]