Add an API endpoint for managing JIRA permission schemes

Presented in user story form:

As a JIRA administrator,
I want a way to programmatically manage permission schemes,
because manually setting for 40+ permissions, and then quadruple checking to make sure I got it right, is a sadness that lingers for the rest of my days administering JIRA

The deprecated SOAP API does provide functionality for managing permission mappings, however it can only assign permissions to Users and Groups. The lack of support for assigning permissions to Roles makes the SOAP API less than useful for managing permissions on modern JIRA instances.

With updated API support, I could automate the creation and enforcement of permission schemes using a configuration management tool such as Puppet or Chef. Less manual editing and associated mistakes.