Refactored JIRA custom field support based on further analysis of JSON return values. Solution is much more generic.

More messaging for missing fields, and only fail on required fields

Add preliminary test for alm_remove_task
 - JIRA only working at present, Rational needs an update to fully enable this
Updates based on review
- Removed .keys() where appropriate
- Only refresh tasks in live testing if the config asks for it, there are cases when a user may not have permission
Merge pull request #194 from sdelements/refactor_jira_custom_field_update_tests

Refactored JIRA custom field support