The router preview item can be specific to the part that is being
tuned, rather than the whole net. It's also less visually noisy as
it doesn't dim/undim the rest of the board.
Using kigfx preview items for the status keeps us from having a bunch
of focus issues with the status popup window.
(It's still leaking into BOARD_COMMIT and some other places, but at
least it no longer leaks into all the edit tools.)
Also fixes some bugs when moving/copying/pasting multiple selections
containing length-tuning patterns.
Jeff Young
Graham Keeth
Alex Shvartzkop