Removed obsolete namespace dependency.
Added a predicate for "ping" messages.
Ping handling for WebSocket connections.

Asynchronous, periodical emission of ping messages
to the connection's client.

Handling of incoming ping messages from the connection's
client.
Message content accessor method for "ping" messages.
Seperated creation of "ping" bytes from sending them.
Published some members of the "connection" api.

Will be required by the "ping-pong" module.
Scheduling of "ping" sendings from the server to the client.

Periodic sending of pings, handling of the corresponding pongs.
Detailed logging of ping sendings.
Log incoming pings (handling not yet implemented...).
Fixed wrong args in "deliver" call.
Use the ping/pong support for connections in the file upload app.
Enable logging for "ping-pong" module.
Defined a constant for the ping delay in seconds (currently 30).
Send a "pong" message (as response to an incoming ping).
Implemented handling of client pings.
Generate the mask bytes directly into a byte array of length 4.
Allow the start index to be specified and marked function as "destructive".

Appended a "!" to the function's name to indicate that it's destructive
wrt the given byte array, i. e. it modifies the array's contents in place.
Use the "->>" macro to prepare for more exprs. to be chained.
BUG FIX: wrong start index for iterating through the mask bytes.

Must always be zero, not  equal to the start index for the bytes to
be masked!
Use raw byte arrays when assembling messages to be sent to the client.