Improvements for querying mechanism for MappingsController and ExtendedMappingsController

Purpose/Overview:

• Response body of GET /mappings, GET /extended-mappings and GET /extended-mappings/locations endpoints should contain actual total records count.
• Replace DELETE /extended-mappings endpoint with DELETE /extended-mappings/remoteStorageConfigurationId/originalLocationId to allow deleting of specified original location
• Update GET extended-mappings/locations endpoint to filter remote locations by remoteStorageConfigurationId query parameter

Requirements/Scope:

• GET /mappings, GET /extended-mappings and GET /extended-mappings/locations endpoints are updated
• DELETE /extended-mappings is replaced with DELETE /extended-mappings/remoteStorageConfigurationId/originalLocationId
• GET extended-mappings/locations endpoint is updated

Acceptance criteria:
Unit tests are updated (to cover at least 80% of code)