Remove level hack in half_life()

Also skip over unused datasets and use direct float conversion of
energy level.
constrain level continuation parsing so unknown br's aren't returned
get rid of unused _level_regex and refactor _level_regex2 to _level_regex
remove duplicate levels in half_life() test
return keV instead of MeV from level_record
number levels by energy not by metastable state number

Also update tests accordingly
fixes to origen_data for updated level record parsing

adds state and fixes the test to check for levels in keV not MeV
Add final ensdf record parsers
Add all decay types to decay dataset
Add br to decay dataset so alphas can be normalized
associate x-ray with radiations instead of decays
fix for multiple continuation records
Fix x-ray calculations for electron capture
refactor atomic_decay to decay

Also moves data to a new decay group in preparation for more ensdf data
Merge branch 'staging' of https://github.com/pyne/pyne into ensdf2
Addition of more ensdf data to nuc_data
fix imports and dataset building bugs
Fix speed and build issues.
fix indentation and state cutoff
Add more detailed data description to tables