Create descriptors for source and sink connector for catalog purpose

[oscerd]

To be able to collect all the connectors, we need to create files similar to component.properties in plain camel.

Since we have an id for each connector of this kind: camel-component + connector-type, we need to create at most two descriptors one for sink (if any) and one for source (if any).

This descriptors will be in src/generated/descriptors

During the catalog generation, we'll need to parse these files and create connectors.properties file like the components.properties for plain camel.

Related to #430