bug fixes and restart i/o for spatial mode

(1) bugs in 'restart': soil layer 'frozen' state added;
(2) for spatial-mode: monthly restart is not read from file anymore, but
from a deque for all grids (or cohorts).
(3) spatial-mode calling loops: year, month, and cohort are in one, as
Alec suggested.

N.B. my testing on cygwin shows memory leak - needs re-check.