Modify naming and attributes of time variables on history files to be consistent with other CESM components

[billsacks]

See ESCOMP/CESM#194 and especially the google doc referenced from ESCOMP/CESM#194 (comment)

The proposed changes for CTSM are:

Land current output:

	float time(time) ;
		time:long_name = "time" ;
		time:units = "days since YYYY-MM-DD HH:MM:SS" ;
		time:calendar = "noleap" ;
		time:bounds = "time_bounds" ;
	double time_bounds(time, hist_interval) ;
		time_bounds:long_name = "history time interval endpoints" ;

Land proposed output (Changes made: time changed to type double, 2nd dimension name of time_bounds changed to nbnd to match CAM, added units/calendar attributes to time_bounds array, changed time_bounds@long_name to time interval endpoints):

	double time(time) ;
		time:long_name = "time" ;
		time:units = "days since YYYY-MM-DD HH:MM:SS" ;
		time:calendar = "noleap" ;
		time:bounds = "time_bounds" ;
	double time_bounds(time, nbnd) ;
		time_bounds:long_name = "time interval endpoints" ;
		time_bounds:units = "days since YYYY-MM-DD HH:MM:SS" ;
		time_bounds:calendar = "noleap" ;

[slevis-lmwg]

I'm tentatively assigning this issue to @samsrabin based on this morning's conversation. Assignment may change after we meet with @billsacks

[ekluzek]

To be complete the calendar attribute should also be added to: mcdate, mcsec, mdcur, mscur.