NDSize: add conversion to bool operator (rank > 0)

Basically the inverse of empty()
[test] DataSet: Test for NDSize's bool conversion operator
DataSpace::create: Use NDSize's bool conversion
DataSpace::create Use const ref instead of pointer for maxdims
[test] DataSet: omit unnecessary parameters in DataSet::create

In TestDataSet::testDataType() when we are creating the dataset
don't set the last two parameters explicitly.
DataSet::create<T> remove maxdims and chunks parameters

For maxdims use h5S_UNLIMITED instead and and for chunks do a guessChunking. It was nowhere used differently in the codebase.
DataSet::create Add maxSizeUnlimited, guessChunks params

Both are boolean and default to 'true'. If maxsize parameter is not
present but maxSizeUnlimited is true set maxsize to unlimited.
If chunks is not present but guessChunks is true we will use
DataSet::guessChunking() to infer the chunking.
DataSet::create make maxsize & chunks parameter optional

This is for the H5::DataType overload. Default to nullptr as in the
nix::DataType overload.
[test] DataSet: remove now unnecessary params in ds::create
PropertyHDF5: Use DataSet::create default params

Make use of the new default parameters of DataSet::create.
DataSet::create remove maxsize and chunks parameter

This is for the non-template overload that takes a nix::DataType
DataSet::create: convert maxsize, chunks param into const ref.
Merge pull request #119 from gicmo/ndsize_bool_conv

Cleanup DataSet::create usage in the project

LGTM