v0.10.6: Improved Docker, added `%capture`

• Feature request #138
  • Added openssh-client, rsync and curl, to allow users to install other dependencies.
  • Added sudo for apt install and apt update.
  • Added support for autostart.sh that if present in the mounted container /notebooks directory, and if root owned
    and set as executable.
• Updated Dockerfile to latest version to JupyterLab -- now the base docker is served quay.io/jupyter/base-notebook
• Added %capture [-a] <file> to capture the output of a cell (#142)
• Fixed nbexec: added --disable-gpu and --disable-software-rasterizer when executing "headless" chrome for tests.