Fix some sensors in menu showing as blank (LP bug #1207138)

Seems we now need to set menu item text / icon before we
add it to the menu otherwise it ends up blank
Fix bug where primary sensor changed unexpectedly

When disabling ANY sensor we would pick the top-most menu-item to be the
new primary sensor - instead this should only happen when the primary
sensor is disabled - fix to make it so.
Update .gitignore