added parsing for date range.
Merge pull request #239 from nla/feature/acm-dsc-85

Add new fields required in ILMS to amber.
additional EAD fields and dates parsing.
additional EAD fields and dates parsing.
Updated date range parsing and its unit test.
merge in changes.
updated to include review comments.
use locally defined month enum for now.
added more date ranges for testing date parser.
Merge pull request #240 from nla/dsc-807

Dsc 807
Revert "Add holding number."

This reverts commit cacd2e1a9b1afcf5bc66843e3717e14ec5f7d8c8.
Merge branch 'master' into feature/acm-dsc-85