Details:  exclusive motions seem to require extra thought

Task:     Found by Sebastian while adjusting Bitrock
RevBy:    Sebastian
AutoTest: None
Details:  -

reported by J Hseu

    Details:  also rename 'atEol' to 'atEndOfLine'

    Details:  tank count() into account, fix cursor positioning after undo

    Details:  fix behaviour of 'r'

    Details:  was not recorded onh the undo stck

    Task:     180315
    RevBy:
    Details:

    Details:  prevent creation of empty "groups" that required
additional 'u' key strokes to 'undo'

    Details:  was broken due to wrong cursor selection approach

Many singletons have their own instance() method, in which case there is
no need to use ICore::instance() to get access to them.