split JIRA lib in jira and jira_misc

Current the JIRA REST API is partly implemented in jira.sh:
https://github.com/nuxeo/integration-scripts-priv/blob/master/libs/jira.sh

But on top of the official API, some custom functions to deal with Nuxeo-specific use cases have been added.

Ideally the JIRA REST API should be in jira.sh and additional functions in jira_misc.sh.

The following functions should be in jira_misc.sh:

getProjectVersionId
getVersionReleaseNotesUrl
getHFReleaseIssue

At the same type of the split, some cleanup could be done like:

1. follow Shell function naming conventions and update the scripts using those
2. replace the last occurence of json_pp with jq .
3. add Nuxeo headers to both libs