docs: J-Link commands added to the manual

docs: J-Link commands added to the manual

The J-Link related commands and configuration commands were added
to the "8.2 Interface Drivers" section of the manual.
(previously they were enumerated as comments).
The 'jlink pid' was marked as Config all other as Command.
A draft of a compatibility note was added, but probably
a table would be more appropriate.

Change-Id: Ifbe230706815196aaad4e3729ed5089d5088b769
Signed-off-by: Liviu Ionescu <ilg@livius.net>
Reviewed-on: http://openocd.zylin.com/680
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>