FakeVim: Correct behavior of command "D" in visual block mode

Command "<C-V>...D" deletes characters inside and behind
block selection.

Change-Id: I2589bc560306a9a5a893f810c8c8037f44517af7
Reviewed-by: hjk <hjk121@nokiamail.com>
FakeVim: Added helper function to retrieve character at a position

Change-Id: I9798adeec3b92f093a275d0af885a4546b4c545c
Reviewed-by: hjk <hjk121@nokiamail.com>
FakeVim: Text cursor is thin when selecting text with mouse

Task-number: QTCREATORBUG-12809
Change-Id: I2b2e5cdbd8ab332e1bd05fb5c7857409318b736f
Reviewed-by: hjk <hjk121@nokiamail.com>