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¶

ref #7010 Disable multi selection for all tree viewers (temporarily)

ref #6925 Open term editor in editor area

ref #6925 Fix some FIXME E4 tags

ref #6925 Inject context into operations to allow sync/async execution

ref #6925 Fix part initialisation for open handlers

ref #6922, #6925 Close editors when reconnecting

ref #6922 Update title of term editor