Added LSD funcionality

Added functionality to filter out lines based on their orientation and size. 
Finding point of intersection of 2 lines.
Documentation updated.

The four added functions are:
1. intersection: Returns the point where the 2 lines intersect (as long as they are not parallel).
2. filterSize: From an input vector of lines, generates a new, that contains those segments that are in the size range.
3. retainAngle: From an input vector of lines, generates a new, that contains those segments that are in the angle range.
4. filterOutAngle: From the input vector, returns those that are outside the angle range. E.g. when someone wants to remove all vertical/horizontal lines and keep the rest. 

In order not to duplicate code in 3 & 4 a helper function is doing the filtering, and a parameter determines whether to keep or exclude the line. Technically they can be combined, but that would expose one more enum. 

Fixed typos in the previous documentation.