Added OpExportMultipageTiff
Added OpExportMultipageTiffSequence
OpExportSlot: Added support for multipage tiffs and multipage tiff sequences.
Added OpZeroDefault (with test)
OpFormattedDataExport: Provide appropriate ImageToExport.meta.drange value if the user gave normalization parameters.
Merge branch 'multipage-tiff'

Conflicts:
	lazyflow/operators/ioOperators/opFormattedDataExport.py
Removed most trace logging per ilastik issue 472.
tests: Skip InterpolatedFeatures test on Travis-CI.
OpValueCache: Handle Request.InvalidRequestException correctly.
OpMultiArrayStacker: Use slot.ready(), not slot.connected() to determine readiness.
OpArrayCache: Removed an unused function.
OpBlockedArrayCache: Added a FIXME for parallel requests.
Auto-import lazyflow.slot
OpReorderAxes: Allow temporary invalid axis order, but assert if the user actually tries to execute the operator with invalid settings.
fixed ilastik/ilastik#557; fillmissing can be tested
Merge pull request #103 from burgerdev/pr-fillmissing-validation

fixed ilastik/ilastik#557; fillmissing can be tested