merge duplicate search and summary text input when creating issues

[Karl-Philipp Richter]

When a new report is created there's a "Summary:" text input with a "Check again" button next to it for checking for duplicates and a "Summary:" text input which is used for the actual summary of the issue report. They can be merged and the check for duplicates can be triggered after content change (with a delay to save query resources) of the one text input.