KisPrescaleProjection::updateCache should not depend on ant UI data

So now it doesn't fill in the KisUpadteInfo fully, it just saves the
dirty image rect in it and fetches the data. All the UI related actions
are performed in KisPrescaleProjection::recalculateCache.

Added some unittests for KisPrescaleProjection, including the testcase
for bug 289915.

CCBUG:289790
CCBUG:289915