Pyinsane

- Windows/WIA: Fix build
- set_scanner_opt(): Fix exception raised when trying to set an option that is
not active

- Add MANIFEST.in (.cpp and .h files were not included in package ...)

- pyinsane2.set_scanner_opt(): Check the option is active before trying
setting it
- Change slightly the output str(scanner_device) (remove useless "Scanner: ")

- API has been redesigned so it can handle backends other than libsane (rename
SaneException into PyinsaneException, etc)
- Add support for Windows Image Acquisition API (v2)
- pyinsane2.init() + pyinsane2.exit() added
- pyinsane2.sane.abstract_th removed

- Add a workaround for Sane driver crashes and memory corruptions ('abstract_proc')
- Python 3 support: Constraints must be str() objects, not bytes()
- OS X support
- Rawapi: Fix: When Sane is not available, 'import pyinsane.rawapi' should actually work, but pyinsane.rawapi.is_sane_available() should return False
- RawApi: Fix mistake preventing authentication
- Methods '__del__' removed on Pyinsane's objects

- Fix scan from feeder (multiscan)