Provide Transient Properties on netCDF Library

[kprussing]

CMake provides the means to track the transient dependencies of a library, like its include directories, by setting the appropriate property on the target(s). This pull request does two things. The first add the include directories to the netcdf library so that downstream usage only requires adding the link library. Specifically

add_executable(myprog ...)
target_link_libraries(myprog netcdf ...)
target_include_directories(myprog ${netCDF_INCLUDE_DIRS} ...)

becomes

add_executable(myprog ...)
target_link_libraries(myprog netcdf ...)

This helps CMake to correctly track the implicit dependencies and get linking orders correct.

The second change (second commit) is adding a namespace for the netCDF targets. Namespaces are advised by most tutorials (I'm thinking this one in particular), but are in reality not critical.

Closes #1539

[CLAassistant]

All committers have signed the CLA.

[WardF]

Thanks!

[kprussing]

It just dawned on me that I might have gotten in my own way with the namespacing. The second commit could break downstream builds that rely on the library being named netcdf. I should do a couple more checks before you merge this back to master. I'll check when I get back to the office in the morning and update with my findings (or tonight if I need to fiddle ;-))

[kprussing]

I just checked, and CMake usage works with both netcdf and the namespaced version netCDF::netcdf in a target_link_libraries. So, merging should not cause issues with downstream projects.

As a followup, should a note on usage with CMake be added to a particular part of the documentation? This pull request notes how to use netCDF in a CMake build, but I don't see anywhere in the documentation that looks appropriate.