Update Subsurface to 4.9.3
Changelogs available here
Packaging change: Switch to github source
Planned a short dive with three planner points, saved and re-loaded the dive and continued editing
Note: This still has no google maps plugin, as discussed here: https://dev.getsol.us/D4811
Also fixes the error on launch with the current package (because of outdated libgit reference).