Make the type-in search in the Parent LInk field to work in the same way that Epic Link field (to keep consistency of Jira application across plugins)

The automatic search performed when typing an issue and which provides suggested items in the Parent Link field (Jira Portfolio Plugin) works in a different way than when the same action is performed in the Epic Link field (Jira Agile).

Additional Details

The way each automatic search works is detailed below.

Parent Link (Jira Portfolio Plugin)

• It only finds a valid suggestion if the complete term is specified and hence
• No partial search when specifying the project key
• No highlighting when partially finding a suggestion
• It only highlights a term if it is the complete term and matches
• No partial search when specifying terms that are in the initiative's summary
• It uses an API request as

  http://localhost:8080/rest/greenhopper/1.0/epics?searchQuery=&projectKey=NKP&maxResults=100&hideDone=true&_=1538899315928
  

Epic Link (Jira Agile)

• It searches and starts suggesting epics with a part of the issue key (for example with just the project key)
• It highlights what it matches (partial term) in the suggestion
• It can search for either the issue key or the Epic name field
• It does not search for the summary field
• It uses an API request as

  http://localhost:8080/rest/jpo/1.0/parent/suggest
  

Expected behaviour

Ideally both searches would work in the same way, since these two fields have a similar functionality.
End users found that Epic Link search easier to use, hence this feature request.