Add yellow (green) and red temp lines to CCD temperature plot

The limit values are read from the characteristics.yaml file.
starcheck.pl now passes the location of that file to the Python.

There's also a plot change here to try to make the load start time
line more apparent (width increase / color change).
Merge pull request #74 from sot/add_limit_lines

Add green horizontal line at -15 on temperature plot (red at -14)