Add gesture recognizer

1. Use polymorphsiom to add different recognizers
2. Modify all the application to choose different recognizers
3. All recognizer have to add the test model
4. Modify the FStrip.java to record the contour path
Use linear interpolation to estimate gap radius

1. Divide the gap to n part
2. The radius of ith part is (i/n) * r1 + (1-i/n) * r2
3. Since radius would not be contiunous as the strip is almost flat, I used harmonic average
4. Adjust the zeroing threshold from 50 to 5 to let the data more concise