KateStatusBar: Add dictionary button

Summary:
...to indicate the current dictionary and for the handy access to the
spell check menu, which is enhanced to offer the user preferred
dictionaries

Test Plan:
From shot to shot is only the cursor moved. The dictionaries was set previously.

Reviewers: KTextEditor, cullmann

Reviewed By: KTextEditor, cullmann

Subscribers: cullmann, ngraham, dhaumann, kwrite-devel, kde-frameworks-devel, KTextEditor

Tags: Kate, Frameworks

Differential Revision: https://phabricator.kde.org/D18125