Fast drop and fast rise alert + upload sensor age to NS + fixes

New feature: Add fast drop and fast rise alerts (contribution by Oliver Searle-Barnes)

enhancement #53 upload sensor age to nightscout

fix #61 Wrong way to determine the Bubble hardware (not visible for user)
fix #62 XDrip is crashing after loosing the connection with Blucon
fix #63 crash when alert value given by user exceeds Int16 range
fix #64 crash when user gives invalid value in calibration textfield
fix #68 calculation of diff with previous value not correct if readings less than 5 minutes apart