URxvt: Disable PrntScr key, very annoying.
Vim: set textwidth={ 78 => 120}
Vim: Re-map <F1..4> keys.

This commit remaps Vim commands to <F1..4> keys. <F5..> keys are
reserved for plug-ins.

Add a toggle for ':help ignorecase' on <F3>.
Move <F7> to <F4>.
Vim: Silent sane navigation.

This is needed as sometimes console Vim gets stuck and starts printing
out the 'g{k,j}' keys. Annoying.
Vim: Drop 'very magic' regular expressions.

The mapping very actually worked properly and very magic is very
confusing anyway.
Vim: Use 'unnamedplus' register, be explicit about clipboard settings.

This commit enables integration with the X11 clipboard in all operations
where a register is not explicitly specified.

The commit also explicitly specifies the clipboard settings, see
':help clipboard'.
Vim: Make Y consistent with C and D. See ':help Y'.