Fixes for gp3 algorithm

[puzzlepaint]

Line 229: The intention of the code seems to be to check whether any edge leads to visibility == false and then break. The visibility check seems to be inverted in this line, though. Compare this to lines 225, 472, and 478.

Line 423: angleR is computed from angles_[i].angle, which is computed using atan2. This function's return value range is [-M_PI, M_PI]. angleR is later compared to angleMin and angleMax, which are computed from angle1 and angle2, which are also computed using atan2. Therefore I think that the wrap-around check should be at M_PI, not 2*M_PI.

Line 1482: There seems to be a typo where a = is missing in a comparison such that an assignment is done instead. Compare this to the analogous line 1459.

I think there may also be a bug where the connectPoint function adds a triangle in a place which is designated as a gap by the triangulation function, and then the ffn_/sfn_ are not updated correctly there, but I'm not sure and I don't have a fix for that.

I tested the changes using test_gp3. The result is nearly identical to before.

Original result: https://drive.google.com/open?id=0Bxrkk2CLB8MbQXdZWDBDNHJ1UlU
With this PR: https://drive.google.com/open?id=0Bxrkk2CLB8MbVTVDYnR3czUtV00
(Image upload to github did not work for some reason.)

[puzzlepaint]

It seems like some unrelated tests are failing in the CI.

97% tests passed, 2 tests failed out of 67

Total Test time (real) = 349.47 sec

The following tests FAILED:
	 16 - common_io (Failed)
	 30 - feature_shot_estimation (Failed)
Errors while running CTest
make[3]: *** [test/CMakeFiles/tests] Error 8
make[2]: *** [test/CMakeFiles/tests.dir/all] Error 2
make[1]: *** [test/CMakeFiles/tests.dir/rule] Error 2
make: *** [tests] Error 2

91% tests passed, 2 tests failed out of 23

Total Test time (real) =  99.23 sec

The following tests FAILED:
	 11 - a_registration_test (Failed)
	 12 - registration_api (Failed)
Errors while running CTest
make[3]: *** [test/CMakeFiles/tests] Error 8
make[2]: *** [test/CMakeFiles/tests.dir/all] Error 2
make[1]: *** [test/CMakeFiles/tests.dir/rule] Error 2
make: *** [tests] Error 2

[taketwo]

Hi, thanks for the fixes. I'm not familiar with the algorithm, but I had a close look at your changes and they all make sense to me. Since the unit test still passes (though it's coverage is probably not complete) I'd vote for merging. @jspricke @SergioRAgostinho your opinion?

[SergioRAgostinho]

Sorry I was late to the party but I agree on the changes proposed and the explanations provided, albeit also being unfamiliar with the original implementation.

@puzzlepaint Thank you for the images. 👍