Simple kinematic robot arm program

Solves a simplified 2D inverse kinematic problem for a robot arm with 'n' links of variable lengts 'r'. Needs to be complemented with the 'cylinder2P' program created by Per Sundqvist (https://www.mathworks.com/matlabcentral/fileexchange/5468-cylinder-between-2-points) or a similar function. In the script I have rewritten the 'rotate' function from Matlab and called it 'rotate_eff' (as in "efficiently"). But you could simply change that back to 'rotate'.