Add type hint to DataBinding about which type is expected

[Christian Oeing]

This type hint could make the handling in the inspector much easier:

• Only show context properties that are compatible
• Only show references that are compatible
• Only allow providers that are compatible (this would require a hint on the data provider as well about which type it provides)

Instead of not allowing incompatible values there could be a warning as well to start with. The selection should be made smaller anyways, so in the common case the user can choose more quickly.

[Christian Oeing]

Increased priority as this is a common source of mistakes that non-programmers make when they connect the scripts on Unity side (selecting the wrong script from the dragged game object)

[Christian Oeing]

Added type hint to only show references that are compatible

[Christian Oeing]

Type hints to filter the context properties are not that high prio as there are many situations where the value can be casted. I'll create a new issue once this gets urgent with a specific use case.

[Christian Oeing]

Use a first type hint for data providers, so only components that implement IDataProvider can be assigned.

[Christian Oeing]

For the last idea (only allow data providers with the desired type) the new issue #71 was created.