two-ASIC support added

Implemented support for two ASICs in the FPGA logic. Therefore, the
exposure object has been upgraded to handle 80x160 images instead of
80x80.

There seems to be an additional peak in the histogram around 2000 ADU
that wasn't expected. I am still investigating this.
Merge pull request #3 from kjgregory/master

two-ASIC support added