Merge pull request #1 from Cadair/master

Modifications to hdf and helpers.
Merge pull request #2 from Cadair/master

Changes to field_types to allow writing all the field_types in one call.
Merge pull request #3 from Cadair/master

a bit of a refactor
Merge pull request #4 from Cadair/master

examples and beta main dataset writers.
Merge pull request #5 from Cadair/master

More tidying up, made two new high level wrappers.
Merge branch 'master' of github.com:Xarthisius/fgdfio
Merge branch 'master' of github.com:Cadair/fgdfio
Start work on a dataset reader