More mapping options

[bartaz]

Somewhat similar to #35 it would be useful to have an ability to map GH labels to different Epics in JIRA (as mentioned in #35) or to automate assigning JIRA labels based on GH labels.

Currently the only mapping possible is labels to issue types, but if we have different categories of issues (that could map to different epics/components/labels in JIRA) there is currently no way to automate this mapping, and it has to be done manually in JIRA after issue is synced.