Add a makefile to bootstrap the repository

Simply do a `make` inside the cloned repository directory. That will do
two things:

- download and install a virtualenv inside the `env` subdirectory;
- install the needed pre-requisites in order to successfully run the
  `build` script without the need to install any package system-wide
Ignore `env` subdirectory
M-x whitespace-cleanup (remove tabs)
Fix dev server invocation
Remove tabs & reindent
Add twisted to the requirements
Cosmetic changes
Remove tabs & reindent
Add doit recipe to recompile scss files
Draft version of the sidepanel actions features