Update .travis.yml

fix script
add some value representations in DICOM
Merge branch 'master' of github.com:DerOrfa/isis
test ch_propmap in travis as well
change load interface of IO-Plugins and rename IOFactory::load=>IOFactory::loadChunks
Merge branch 'master' into api_change
Merge branch 'api_change' into ch_propmap

Conflicts:
	lib/Core/DataStorage/io_factory.cpp
	lib/ImageIO/imageFormat_compressed.cpp
	lib/ImageIO/imageFormat_png.cpp
move Value::toString to ValueBase to reduce API-Bloat
add optional return-list for rejected files in load-functions
Merge branch 'api_change' into ch_propmap

Conflicts:
	lib/Core/CoreUtils/value_base.cpp
	lib/Core/CoreUtils/value_base.hpp
	lib/ImageIO/imageFormat_nifti_dcmstack.cpp