Improvements to peak filter GUI
This merge request addresses issues #58 (closed), #61 (closed) and #65 (closed).
- In preview panel peaks were surrounded by a red outline, so the peak colour (green for caught by filter, red for rejected by filter) was impossible to distinguish when zoomed out. Switched to QPen::transparent when filtering.
- Added count of number of peaks caught by filter to header of peak table.
- Added strength column to peak table.
- Changed maximum value of minimum strength 1000->10000 since the range 0-1000 wasn't enough to appreciably change the number of peaks caught.