Add support for alpine images (has newer ffmpeg)

api/build_config.py

build_pipeline_generator.py

common_py/build_config.py

job_controller/build_config.py

job_controller/jobs/base/build_config.py

job_controller/jobs/base/run.sh

job_controller/jobs/ffmpeg_base/build_config.py

job_controller/jobs/media_process_scheduler/build_config.py

job_controller/jobs/move_file/build_config.py

job_controller/jobs/rescale_video/build_config.py

job_controller/jobs/sample_thumbnail/build_config.py

job_controller/jobs/source_file_sorter/build_config.py