gr-fec - LDPC: Clean up, and adding LDPC to BER curve gen example.

- The 6 alist files are just being re-pushed. git is saying they were modified on the remote but I didn't modify them, and couldn't solve that mystery.

- CMakeLists.txt being updated to install the python script that generates matrices for use with LDPC encoder. Also it copies the alist files to python2.7/dist-packages/gnuradio/fec/LDPC

- Adding the LDPC encoder/decoder to the ber_curve_gen.grc example. Note: the resulting plot shows LDPC performance as worse than the dummy encoder/decoder; so, still more work to do....

- Slight mod to the bit flip decoder to convert incoming floats to 0s and 1s, in the same manner as the repetition decoder.