Fix build on OS X using all external libraries (except xerces)
Add installation command for easier packaging in future
Fix building on Linux using all external libraries (except xerces)
Build python module on sandbox.
Macros to build python module on sandbox.
Add options to build appleseed components.
Merge pull request #223 from est77/est

Small CMake related improvements.
small code simplification.
Merge branch 'master' of github.com:jupiter-jazz/appleseed
fixed deployment of _appleseedpython.dll and __init__.py to the sandbox on Windows.
added a clarifying comment.
Added more directory to be installed so that the package is more complete.
added a sample renderer to debug tile renderer issues such as half-pixel shifts, etc.
significantly reworked and improved the adaptive image plane sampler.

- improved the noise evaluation algorithm
- replaced the max variation criterion by a quality knob
- got rid of the max contrast criterion
fixed major bug in adaptive image plane sampler.

- the samples need to be scaled to account for the varying density of samples per pixels.
- moved variation tracker into its own file and added a test.
- simplified code.
factorized some code between the uniform and adaptive image samplers.
several refinements to the Render Settings dialog.

- confirm changes when switching to another configuration.
- restore widgets values when canceling the dialog.
fixed crash (introduced in previous commit) when loading a scene after having opened the Render Settings dialog.
the watch_folder.py script can now forward additional, user-supplied arguments to appleseed.
tweaked comment.
the alpha mode of a texture instance may now be set to "detect": the renderer will try to guess which alpha mode to use based on the actual texture contents.