Ray tracing

## New submission: ray_tracing

This submission includes:
ray_tracing.{c,h} and all the necessary ingredients:

1. calibration.{c,h} (see previous submission)
2. lsqadj.{c,h} 
3. parameters.{c,h} (Important - it is required for other things)

### Tests:

Test project /Users/alex/Documents/PTV/alexlib-openptv/liboptv/build
    Start 1: check_fb
1/3 Test #1: check_fb .........................   Passed    0.01 sec
    Start 2: check_calibration
2/3 Test #2: check_calibration ................   Passed    0.01 sec
    Start 3: check_parameters
3/3 Test #3: check_parameters .................   Passed    0.01 sec

100% tests passed, 0 tests failed out of 3

Total Test time (real) =   0.05 sec