zshrc, keys: Reorganise keyboard setup

This commit causes zsh to use smkx mode while its line editor (zle) is
active. This might break backwards compatibility with older
customisations, that rely on binding hardcoded escape sequences to
widgets.

Doing this is _absolutely_ required to make the values from $terminfo
valid. Those might otherwise be wrong and absolutely useless.

We do turn off smkx mode again when the line editor is done. So, nothing
else should be affected.

This commit also reorganises much of the setup, because different
aspects were addressed in between one another.

Signed-off-by: Frank Terbeck <ft@grml.org>
zshrc, keys: Move bindkey calls to the right place

Signed-off-by: Frank Terbeck <ft@grml.org>
zshrc: Load zsh/parameters module

Signed-off-by: Frank Terbeck <ft@grml.org>
zshrc, keys: fix `zrcgotwidget()' function

Signed-off-by: Frank Terbeck <ft@grml.org>
zshrc: Use zrcgotwidget in appropriate places

Signed-off-by: Frank Terbeck <ft@grml.org>
zshrc: Remove old reverse-menu-complete binding

Signed-off-by: Frank Terbeck <ft@grml.org>
zshrc: Fix `salias' wrt parameter scope

Signed-off-by: Frank Terbeck <ft@grml.org>
zshrc: unfunction less utilities

Signed-off-by: Frank Terbeck <ft@grml.org>
zshrc, keys: Move all bindings over to bind2maps

Signed-off-by: Frank Terbeck <ft@grml.org>
grmlzshrc.t2t: Add customisation note about smkx and rmkx for keybindings

Signed-off-by: Frank Terbeck <ft@grml.org>