[test] Benchmark: rng.next_block() returns NDArray
[test] Benchmark: BlockGen takes NDSize blocksize
[test] Benchmark: make_block() returns NDArray
[test] Benchmark: remove vector<T> from make_block
[test] Benchmark nix::dtype_dispatch can return
[test] Benchmark: make_block does not depend on T
[test] Benchmark: BockGen does not have T param
[test] Benchmark: make BlockGen single threaded

And change how it works: Preallocate bufsize blocks and
then randomly return one of these on next_block().
Merge pull request #394 from gicmo/bench_ndarray

Benchmark: de-templatize BlockGenerator
DataArrayHDF5: handle count == {} when reading
Hydra: handle resize for scalar values correctly
TestDataArray: test for reading of scalar values
Merge pull request #397 from gicmo/issue_396

Fix reading of scalar values
add retrieveFeatureData for Tags to util::dataAccess
add retrieveFeatureData for MultiTags in util::dataAccess
add test for feature data access
etended test to check for data access of tags that point to slices
TestDataAccess: initials for feature data for multiTags
add retrieveFeatureData method to MultiTag
add retrieveFeatureData method to Tag