
Proposed file placement
----------------------

All 1D variables (including time CV) -> master
static && not-compressed && size < max_ele_per_master -> master
everything else -> /coords or /data as appropriate

Notes
-----

+ Need to change append definitions to only allow appending of additional
time steps (this is what NetCDF supports)

+ For NetCDF implementation the time dim should be unlimited.

+ It might be desirable to copy small CVs (e.g. time) to data and coord
variable files, but no way to ensure that these stay in sync with what is
in master file. Forget this!

+ Highly desirable that files can be operated on without master,
albeit with some limitations.

+ PutVar and GetVar() don't have way to specify compression level
- Does variable need to be opened ?

+ need to test VarBase assignement operator and copy constructor work
for derived class i

+ Need to define meaning of \p reflevel. If it's kept compatible 
 with VDC2 then we are precluded from having varying numbers of 
 refinement levels along different dimensions

Questions
---------

+ How handle masks/missing-values?

+ Only one time CV?

+ When are NetCDF files "defined"

+ Can append mode be made more general? I.e. allow for adding new variables
to the data set? Seems like this would only impact master file, and would
create reading and re-writing the master file.
See http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-f90/Adding-New-Dimensions.html#Adding-New-Dimensions.
 
+ Implications of append mode wrt defining new or changing existing stuff

+ How are uniform coordinate vars handled wrt what is read/written
and what is actually stored?
