allow import of PDF as full-page in the app

[adamwulf]

when loading pdf:

• single page PDF should immediately import onto the page as if it was an image
• multi page PDF should show menu opened to pdf tab and showing recently imported file
• allow cutting scraps out of a page w/ a background
• ability to add every page from the pdf as a new stack Support multiple stacks #44
• the background on the page should be high fidelity (the pdf reader i have now shows pages at very low resolution, but i should scale up that resolution when rendering it
  • https://developer.apple.com/library/ios/documentation/GraphicsImaging/Conceptual/drawingwithquartz2d/dq_pdf/dq_pdf.html
  • https://developer.apple.com/library/ios/samplecode/ZoomingPDFViewer/Introduction/Intro.html

i need to decide how i should handle pdfs with 1 page vs pdfs with multiples pages

another option would be to import the pdf as the background to a page, but that'd also make it hard to import 2 pages and put the side by side and compare them. i should probably default to scraps, and the user can zoom the scrap to full page if they want.

When cutting scraps out of the base page, I should add a white cashapelayer for each cut. I can then merge those paths on a background thread into fewer shapes of possible.

This is related to multiple stacks #44.

[adamwulf]

the commit in cbcf351d02452b7c4e7800d28411abdba7207f62 has the import file type for the plist

[adamwulf]

I should use the tiled PDF viewer in ZoomingPDFViewer to display the pdf as the page background.

ideally, i would:

• create new PDF with only that 1 page
• save the one page in the page's assets folder
• make page backgrounds abstract so that they don't rely on an image view if its not an image
• render that pdf with the TiledPDFView for the page background

[adamwulf]

duplicate of #1169