Remove duplicate '@' keybind and unused altKey()

Change made in #212 (cannot execute macros using German keyboard) is
too specific. Undo this change and fix it by implementing a generic
way to handle AltGr conflicts ( # 247 ).
Add withCtrlKey() method, check in equals method

Keybinds which use "C-x" will have this flag set to true automatically,
all incoming keys will have this set based on the Operating System info.

Part of a generic solution for #247 (some textobjects broken with
German keyboard).
Retry a key without modifiers if AltGr suspected.

Issue #247 and #212 report that Windows users cannot invoke certain
keybinds if AltGr is needed to press them. For example, Windows reports
AltGr + Q as Ctrl + Alt + @ to vrapper.

Retry any character keys which don't trigger a binding or remap, but
without the control and alt bits set. If that still won't work, it's
likely that no binds were registered for that key.
Merge pull request #260 from albertdev/alt-keybind-support

Fix for AltGr keybinds