Warn when passing unknown driver creation options

[hawahee]

The write function docstring was incorrectly suggesting compression as a driver creation options keyword, but that does not work and has been corrected to compress.

The stringlist util function has also been updated to check the provided dict keywords against a list of supported driver creation options keywords, and warn when the provided keyword is unrecognized. No checking or warning is performed on the values passed together with the keywords. I could not find a list of supported driver creation options in GDAL.jl or ArchGDAL.jl, so I hardcoded a list based on the Creation Options in the GDAL GTiff documentation.

I see that the warpstringlist function calls stringlist. Does it support the same keywords, or is it for a different purpose?

Also, should the stringlist and warpstringlist input argument dict::Dict{String} be changed to dict::Dict{String,String}?

Supersedes #166

[evetion]

Thanks for the PR! Mind if I make a few changes in your branch? The stringlist method should be generic (as it's used for non geotiff stuff as well), but the check for supported keywords is very helpful though.