Test data support

[mrqwer88]

Add support for FASTNETMON_DO_NOT_CALCULATE_SPEED mode and import_configuration.

Could be used with additional yml config like docker-compose.test.yml

services:
  fastnetmon:
    environment:
      FASTNETMON_DO_NOT_CALCULATE_SPEED: 1
      FNM_IMPORT_CONFIGURATION_PATH: /var/cache/fastnetmon/fastnetmon_backup.tar
    volumes:
      - ${FNM_PATH}/seeds/fastnetmon_cache/:/var/cache/fastnetmon/