Fixed calibration save, and two matrix issues within the multiple undistort variants.

[xionluhnis]

Fixed a few things related to issues 175 and 176.

1. Changed the calibration save method to correctly export the vector of vector of points (otherwise it crashes when we try to reload it).
2. Changed the undistort functions to correctly handle the output parameter (by passing it by reference instead of by value, for edge case where it's currently empty) and using the undistorted camera matrix as newMatrix when undistorting points.

[xionluhnis]

Sorry for the double pull request, I messed up some of the logs and removed some changes that were there for debug. I cleaned the history so it only looks like one commit (no extra commits).

Also, I removed the #ifdef USING_OPENCV_2_3 guard because I am personally using circle targets (with opencv 2.4.8), and I don't really see the point of not having the rest available anyway since if it worked before, given that it works now, let's not remove that part of the code.

[xionluhnis]

Since many people are asking for the solution to #175, do you want me to redo the PR with only that fixed?
I assume you did not merge yet because I fixed more than that and the rest (#176 as well as USING_OPENCV_2_3) are not accepted as issues. Plus it needs to be rebased to the latest master.
I can do a new PR if that's what you want.

[xionluhnis]

I rewrote things on my fork, sorry if that messes up other people, but it will be cleaner for merging the pressing #175 issue.

The old stuff is now on my Issue175+176 branch.