added alembic support cmake option
Merge branch 'master' into alembic_option
Alembic is now optional, with a CMake option. Also fixed the OpenEXR but not Alembic case.
Removed unused definitions
Merge pull request #280 from est77/alembic_option

Make Alembic optional, added an external EXR option, removed unused WITH_XXX definitions.
rendernode.py 1.15: tweaked timestamps formatting.
rendermanager.py 1.3: many changes.

- fixed bug in dependency tracking (project files being rendered were not considered when computing dependencies).
- allow to specify a target directory for rendered frames.
- don't crash when the rendered frame files are locked.
- tweaked timestamps formatting.
Merge branch 'master' of github.com:jupiter-jazz/appleseed
the version string now states whether QMC is enabled.
removed redundant blank line.
rendernode.py 1.16: added --print-missing-deps flag.