Corrected several Matlab scripts

[arango]

I continue revising the Matlab scripts:

• Several matlab scripts were corrected to use nc_constant('nc_ulimited') instead of undefined parameter ncunlim. Many thanks to Arthur E. Ramos for reporting this ​problem

• I cleaned and retested initial/d_climatology.m and initial/d_initial.m template drivers and everything is working correctly.

• Corrected several typos in grid/contact.m. We need to use isempty instead of empty native funtions. Many thanks to John Wilkin for reporting these typos.

• I fixed a typo in initial/roms2roms.m and boundary/obc_roms2roms.m. We need to use nc_vinfo instead of nc_varinfo. Many thanks to John Wilkin for bringing this to my attention.

• Added nc_unlimited parameter to nc_constant.m. Also corrected a typo in the error message.