Support for the context-dependent management of a connection's resources.

Resources can be stored in resource stores that have been formerly attached
to a WebSocket connection for a specific context. The purpose of a context
is to provide control over the accessibility/visibility of the related
store.
Defined a fixed set of valid resource contexts: :application and :connection.

Simplified the design to implement just the basic requirements.
Provide a context when storing or accessing the ping/pong resource.
Require a context for resource removal.

Removal of a resource should be restricted to a specific context.
Provide a context when storing/accessing a channel's resource.
Changed name and arity according to revised 'resources' api.
Incremented minor version number for 'fm-websockets'.
Fixed the look-up path (the context must be considered!).
Deleted the stuff that has gone to the "Sidesho Bob" project.