- Handle GRL_RESOLVE_FULL when a certain key can be resolved by several plugins.

  -> Use alternative plugins if the selected one fails to resolve the key.

- Consider using GAsync callback interface for callback implementations.

  -> Also check issues for binding development related to this.

- Consider using the Ethos GObject plugin framework to replace our current

in-house plugin system.

- Multiple-plugin operations (i.e. search by text on all plugins).

- Python bindings

- Consider a more flexible post-processing mechanism for query

operations (browse, search, etc).

  -> We have to figure out if that's really necessary.

- Improve configuration interface

  -> Use strings for config keys