Issue #490: Adding docker dev environment

[KacperWojciechowski]

Docker development environment for CMock

Added the docker configuration and scripts for handling it to give
\contributors an automatic, out-of-the-box setup for working on
the project, along with scripts for easy use and instruction of how
to use it. It is a simplified version of my own portable dev environment,
so it has some additional things like prettier status logs and
pre-configured Vim.

Resolves: #490