Amend Debian Dockerfile to allow build with rust nightly (#84)

* Dockerfile added for Fedora, Alpine, Debian

* Dockerfiles moved to ./contrib/docker, "." filter needed for jq in debian-buster

* Deleted dockerfiles from old dir, "." filter needed for jq in debian-buster

* Amend Debian Dockerfile to allow build with rust nightly

contrib/docker/Dockerfile.debian

@@ -1,12 +1,14 @@
 
 # Use: docker build . -t darkfi:debian -f ./contrib/docker/Dockerfile.debian
 #   optionally with: --build-arg BUILD_OS_VER=slim-buster --build-arg RUN_OS_VER=buster-slim --build-arg RUST_VER=1.60
+#   rust nightly with: BUILD_OS_VER=bullseye-slim RUN_OS_VER=bullseye-slim RUST_VER=nightly REPOSITORY=rustlang/rust
 
 ARG RUST_VER=1.61  # 1.60
 ARG BUILD_OS_VER=slim-bullseye  # slim-buster
 ARG RUN_OS_VER=bullseye-slim    # buster-slim
+ARG REPOSITORY=rust             # rustlang/rust
 
-FROM rust:${RUST_VER}-${BUILD_OS_VER} as builder
+FROM ${REPOSITORY}:${RUST_VER}-${BUILD_OS_VER} as builder
 
 RUN apt-get -y update