Add delay after ANT reset message

Wait 500ms after sending reset message (as per ANT+ spec), before
sending any more host commands.
Change usb_bulk_read() timeout back to 125ms
Move early ANT setup after receive loop is started

Moves the early setup code so that the receive loop is already
running when these messages are transmitted. Doesn't achieve much
at this point, but can visualise the send and receive packet flow
better, and will enable the responses to these messages to be
checked in the future.
Close ANT channels before stopping session

This appears to resolve an intermittent issue with the USB2
stick not responding to reset messages when re-opened.
Postpone ANT debug log close

Don't stop debug log until the end of the receive thread (else the
traffic from the close channel messages can re-open the log file).
Whitespace cleanup (tabs to spaces)
Merge pull request #589 from dresco/ANT

ANT+ reliability fixes
About Dialog Config Tab

.. should only be shown on developer builds. When building
   releases or release candidates and GC_VERSION is being defined
   then don't add the config tab -- it is too `geeky' for the average
   end user and not at all useful for debugging.
Update QT install instructions INSTALL-LINUX

.. since Qt changed the name back to Qt 4.8 rather
than SDK 1.1.