Resolve "Вынести ядро битрикс в отдельный volume"

Closes #3

See merge request !1

add environments, rename jobs

add entrypoint script
add link bitrix and uploads to site
add build script

site on 80 port now

add site directory to /home/bitrix
add nginx and apache configs

add data volume for database
add .env file with variables for docker-compose

add startup stage
add job for backup manually edits on site
separate jobs for building front-end and migrations
update docker-compose: use only 1 container
update documentation in README