.bash_aliases: auto-remove orphan containers

[ukkopahis]

• fix aliases to work regardless of user's current directory (using the'-f' flag instead of changing the directory would ignore a possibly existing `docker-compose.override.yml')
• fix iotstack_build alias to include "--pull --no-cache", as without these there may be cases where everything isn't fully updated.
• add the iotstack_update_docker_images alias to perform the basic container update
• docs/Docker: reword for clarity & typo fixes