Documentation: update "Exporting Dives from Subsurface"

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Documentation: update "Planning Dives"

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Documentation: update "Web Service and Companion App"

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Documentation: update "The Menu and Sub-Menus"

Complete rewrite of the 'Filter' and 'Help' sections.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Bump Makefile version to 3.1

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>