Fix of bug #97
**1) Fixed GROUP:IsAlive()**
Returns if the Group is alive.
The Group must:
* Exist at run-time.
* Has at least one unit.
When the first @{Unit} of the Group is active, it will return true.
If the first @{Unit} of the Group is inactive, it will return false.
@param #GROUP self
@return #boolean true if the Group is alive and active.
@return #boolean false if the Group is alive but inactive.
@return #nil if the group does not exist anymore.
**2) Fixed IDENTIFIABLEIsAlive()**
Returns if the Identifiable is alive.
If the Identifiable is not alive, nil is returned.
If the Identifiable is alive, true is returned.
@param #IDENTIFIABLE self
@return #boolean true if Identifiable is alive.
@return #nil if the Identifiable is not existing or is not alive.
**3) Fixed UNIT:IsAlive()**
Returns if the Unit is alive.
If the Unit is not alive, nil is returned.
If the Unit is alive and active, true is returned.
If the Unit is alive but not active, false is returned.
@param #UNIT self
@return #boolean true if Unit is alive and active.
@return #boolean false if Unit is alive but not active.
@return #nil if the Unit is not existing or is not alive.
**4) Updated all test missions, as this is a core change.**
-- Fixed GROUP:IsAlive()
--- Returns if the Group is alive.
-- The Group must:
--
-- * Exist at run-time.
-- * Has at least one unit.
--
-- When the first @{Unit} of the Group is active, it will return true.
-- If the first @{Unit} of the Group is inactive, it will return false.
--
-- @param #GROUP self
-- @return #boolean true if the Group is alive and active.
-- @return #boolean false if the Group is alive but inactive.
-- @return #nil if the group does not exist anymore.
-- Fixed Identifiable:IsAlive()
--- Returns if the Identifiable is alive.
-- If the Identifiable is not alive, nil is returned.
-- If the Identifiable is alive, true is returned.
-- @param #IDENTIFIABLE self
-- @return #boolean true if Identifiable is alive.
-- @return #nil if the Identifiable is not existing or is not alive.
-- Fixed UNIT:IsAlive()
--- Returns if the Unit is alive.
-- If the Unit is not alive, nil is returned.
-- If the Unit is alive and active, true is returned.
-- If the Unit is alive but not active, false is returned.
-- @param #UNIT self
-- @return #boolean true if Unit is alive and active.
-- @return #boolean false if Unit is alive but not active.
-- @return #nil if the Unit is not existing or is not alive.
-- Updated all test missions, as this is a core change.
