jira-integration: Allow to store a comma-separated list of labels instead of URL

This patch allows the user to store a URL or a comma-separated list of words to
specify the possible labels for the JIRA connector.

FEA: ItEr77S16JiraAndTimConnectorContributionIntegration
jira-integration: Rename jiraLabelUrl to jiraLabels

Due to previous commit, this field could save a URL or a list of labels, so the
name has been changed to avoid misunderstandings.

FEA: ItEr77S16JiraAndTimConnectorContributionIntegration