0.4.0 - Provisional Target Inheritance & Config Data

Main Features:

• add provisional support for configuration data
• add provisional support for target inheritance

Note that this new target support is still experimental, and might change. These changes are backwards-compatible with old target descriptions.

Other changes:

• add --plain option that suppresses coloured output
• display where modules are being installed from
• yotta up now correctly checks for updates to the target description
• the "homepage" property in module.json must be valid if it exists
• various other bug fixes and improvements