Add support for vegcover and albedo

[tbohn]

In 4.2 and 5.0 classic, vegcover optionally can be in the veg_lib and both vegcover and albedo can be in the veg_param file. This needs to be handled in tonic.

This also involves changing the logic for options - currently there is just a flag for global_lai (or lai_index in some cases) but this needs to be replaced by the set {veglib_vegcover, vegparam_lai, vegparam_vegcover, vegparam_albedo, lai_src, vegcover_src, and albedo_src}. global_lai would correspond to vegparam_lai = true and lai_src = from_vegparam.

[tbohn]

This was addressed by PR #40 but for some reason didn't get automatically closed. It can be closed now.

[tbohn]

Wait, never mind. The reason it didn't get closed was because I said it shouldn't be closed yet. The idea being that this issue pertains to the reverse direction (netcdf to ascii) as well as ascii to netcdf, and this hasn't been addressed yet.

[tbohn]

The ascii-netcdf conversion aspect of this issue has been addressed in PR #40. The netcdf-ascii conversion aspect of this issue has been moved into a new issue #44. Thus, this issue can be closed.