Graphene 0.5.0 - New Plugin System

Changelog

• Created a new plugin system for Graphene
• Set auto camelCase in the schema type fields to optional (using graphene.Schema(auto_camelcase=False))
• Added a basic Django Debugger with SQL debug capabilities (a la Django Debug Toolbar, but for GraphQL)
• Improved graphql-django-view version and fixed some related tests
• Renamed BaseType to InstanceType for code clarity
• Refactored Fields and Arguments logic
• Improved ScalarTypes based on ClassTypes