Do not report errors in headless.
Merge branch 'master' of https://Stephane-D@github.com/Icy-imaging/Icy-Kernel.git into develop
* fixed serie selection bug on multi serie image loading (regression).
* fixed headless initialization issues (regression).
* completed new VTK 6 library loading.
* removed IcyLogo component.
* some changes made to the importer interfaces.
* 'open' command can now open any type of file (not only
image) with available FileImporter.
* 'import' command allow now to open data with available Importer.