[WIP] Add ak clone

[hparfr]

$ ak clone to be done at initalization of the project (when there is no git clone done yet).
It will do a git clone --no-checkout in order to minimize the brandwith used during git fetch.
For the moment only short syntax is supported. :

server-tools:
  src: https://github.com/oca/server-tools 12.0
  modules:
     - base_exception