Allow for removal of issues (DELETE /api/latest/issue/{key})

[hmmwhatsthisdo]

(This is mostly an issue to track implementing Remove-JiraIssue until I can get a PR in.)

Expected Behavior

JiraPS should have a method for deleting issues in an automated fashion, as the API has support for it (see #135 and the Jira API Browser)

Current Behavior

No implementation exists.

Possible Solution

Implement Remove-JiraIssue, which wraps a DELETE call against /api/latest/issue/{key}