ref #6925 Set conversation and cdmEntitySession to null for dispose

ref #6925 Dispose conversation and entity session when closing editors

• use session from editor input if provided

avoid widgetIsDisposed exceptions by check of control is disposed

Conflicts:¶

eu.etaxonomy.taxeditor.store/src/main/java/eu/etaxonomy/taxeditor/view/e4/AbstractCdmEditorPartE4.java¶

factual data and media view should be grayed for synonyms

ref #6925 Open distribution editor in editor area

cleanup

ref #6595 Remove exception from editor opening

choose smallest representation for media preview

ref #7056 Generate titleCache for newly created image galleries

ref #7056: add possibility to show preview of the image in media view