Use minImageCount when creating swapchain

[zakorgy]

Currently we have two images for frames (this is a default in gfx). But #80 (comment) shows, that there are cases, when we have to use more than two.
The problem is, that acquiring the next frame with more than two frame images returns a Frame with a random id, not with the current_id + 1 as we expecting it.
NOTE: We use (self.current_frame_id + 1) % self.framebuffers.len() to calculate the next current_frame_id at the moment, but this isn't good for this case.
We have to acquire the next frame earlier, to get the correct frame id.