ch07: add homography example as it is in the book
add cherrypy to setup.txt
ch07: Fix query homography example from the bug.

Two problems:

1. The result indices are 1-based, so subtract 1 to find the right sift
   file. (Just subtracting one from each element right after query()
   doesn't work because plot_results() also wants 1-based indices.)

2. matches was an array of arrays of ints, while the H_from_ransac()
   call needs an array of ints. Add explicit conversion code.