Dockerfile optimization

Created by: IvanBayan

Dockerfile modifications, allow to reduce build time and size.

➜  Part-DB git:(master) ✗ time docker build -t partdb/original . > /tmp/partdb_original 
docker build -t partdb/original . > /tmp/partdb_original  0.47s user 0.29s system 0% cpu 5:20.56 total
➜  Part-DB git:(master) ✗ git checkout docker
M	docker-compose.yml
Switched to branch 'docker'
➜  Part-DB git:(docker) ✗ time docker build -t partdb/optimized . > /tmp/partdb_optimized
docker build -t partdb/optimized . > /tmp/partdb_optimized  0.42s user 0.28s system 0% cpu 2:53.87 total
➜  Part-DB git:(docker) ✗ docker image ls|grep partdb/
partdb/optimized                                       latest              90dc38b9ea00        2 minutes ago       733MB
partdb/original                                        latest              d5d61bf91a22        32 minutes ago      1.15GB

Files/directories permissions is a topic to discuss.