Dockerfile Parts (#428)

* De-duplicate Dockerfiles by using a bash file to concatenate common parts

Resolves #375.

Dockerfiles are still committed to the repo to avoid a dependency on bash.

* Add a CI job to confirm the committed dockerfiles are the currently generated ones

* Create dedicated Dockerfiles per processor network

Ensures the compromising of network-specific dependencies doesn't lead to a
compromise of the build process for all processors.

* Dockerfile corrections

* Correct call to build processor Docker image in tests/processor

docs/Getting Started.md

@@ -5,7 +5,7 @@
 ##### Ubuntu
 
 ```
-sudo apt-get install -y build-essential cmake clang-11 git curl python3-pip protobuf-compiler libssl-dev pkg-config
+sudo apt-get install -y build-essential clang-11 pkg-config cmake git curl protobuf-compiler
 ```
 
 ### Install rustup