Improve code generation mechanism

Description:

Changing generated shade or QML code of effects seems to be very hard because of in-lining the Shader/QML code inside C++ implementation. This can be improved by using a light-weight template engine.

Impact/Value:

• Segregates code generation and logic/model
• Helps with maintainability of current templates
• Helps with maintainability of the composer code itself
• Adding new type of effects will be a lot easier.

Suggested Solution:

1. Add dependency to a light-weight template engine like Inja
2. Move code templates to external files/resources
3. Feed the template with the template and the model it should use to generate the code.