clean-up fence manipulation functions and add test for auto-enablement on copter
update tests to have some FENCE_ENABLE tests
add avoidance minimum and maximum altitude fence
add fence switch test while flying
add FenceAutoEnableDisableSwitch for auto mode 2
add more scenarios for plane fence auto-enable
validate fence rc switch behaviour
check fence autoenable by taking off in guided mode
more FENCE_AUTOENABLE tests
add FenceEnableDisableAux and FenceMinAltAutoEnableAbort
Andy Piper