PEP-8 style fixes

No logical change
Remove some unused imports
Fix typos in comment and code

Add an additional EntityType with the correct spelling of Unknown
but leave the old just in case someone actually used it
Replace .has_key with "in" and more PEP-8 fixes
Add numpy and h5py to setup_requires
ns-convert: define all instance attributes in __init__
ns-convert: Make copy_metdata dtype_by_event static
ns-convert: Rename copy_metdata to copy_metadata
ns-convert: remove unused argument from main()
ns-convert: correct string type for bumpy arrays is 'a' not 's'
Library: rename file argument to nsfile so we don't shadow it
File: fix access to _info (it is _info not info)