[Lib] [PHP] Release v2.0.0

GitHub release

Changelog:

• Big refactorings
• Got rid of psr/log dependency. We now have 0 external dependencies.
• Support PHP 7 by renaming a class named Object
• Expose GET /v1/applications end-point
• Expose GET /v1/installations end-point
• Expose PATCH /v1/installations/:installationId end-point
• No longer use the old Management API URL