cooja TimeLine: double-click too short

250ms is too short an interval to use as a default.  In lieu of making this
configurable or obeying window system overrides, use Windows default 500ms
as the maximum interval.

Closes pabigot/contikix#1

Signed-off-by: Peter A. Bigot <pab@pabigot.com>
cooja RadioLogger: fix misleading column names

"From" and "To" suggest these columns provide the source and destination
nodes of the packet.  They do not; they identify the node that transmitted
the packet and up to two nodes that received it, which are in no way the
same thing as the requested source and destination.  This is particularly
misleading when dealing with broadcast packets.  Rename the columns "TX" and
"RX" respectively.

Closes pabigot/contikix#3

Signed-off-by: Peter A. Bigot <pab@pabigot.com>