Add project based west.yml

[jalinei]

• Modules version stored in state.json now correctly compared with west.yml revision hash
• Add the possibility to provide dependencies through a project based west.yml file.
• Add the possibility to skip large installation times due to default west.yml

Fixes #22
Tested on Ubuntu 20.04, I don't have access to a Windows machine to check classic curses..

Questions from my side :

• I guess I should add the same workaround in clear_deprecated_package than in clean_up to wipe .git folder on windows machines ? I can add that commit when confirmed.
• Is it really necessary to have install-deps.py script called from tool manager ? With the current logic, there is no way to skip the initial download, that encompass all packages defined in framework based west.yml which leads to unnecessary disk space occupation & installation times.
  (Example in Ststm32 platform : https://github.com/platformio/platform-ststm32/blob/develop/platform.py#L124)

My proposal would be to launch install-deps.py only from platformio-build.py, this way a potential local west.yml can be detected and install time can be dramatically reduced (from 3GB+ to approx 600MB in our case).

Opinion :

• I don't really understand the added value of --secondary-installation parameter. I got that it permits to distinguish if script is launched from tool-manager or by platformio-build.py but in practice it does not change much.