calibrate: specific variables and ranged specified

now in lake.cfg you input a list of which variables to vary and hte
range over which they can be varied.
minor edit in calibrate tempalte
calibrate: not all parameters are adjusted
added evenly spaced time slices
intermediate fixes; but there are bigger problems

just fixed:
methanogenesis assignment

need to fix:
- ej for oxygen is 4 not 2!
- carbon usage is not sum_j R_j! It's R_C!
fixed e_j for oxygen primary oxidation
fixed carbon uptake rate
improved data-saving from interactive
added plotting tool
improved plotting tool