CP generators and stacked projects

[T. Modes]

Hi group,

I commited a patch which adds a new cp generator setting (rev 4842).
This setting can use the assigned stack numbers from the new layout
mode.
It runs on cp generator for one image of every stack to connect all
stacks. Then it runs (another) cp generator for connecting the images
of every stack. This should speed up the cp generation step for
stacked projects, even when for some images the key generation step is
running twice.

The setting maybe needs a default setting: e.g. autopano-c-sift and
align_image_stack

Please test it.

Thomas