Add define-vi-motion and define-vi-operator macros, and rewrite vi-mode's operator commands with them.

This aims to make them much cleaner and behave more consistently.

Bugs fixed

• Fix dh, ch, d^ and c^ not to delete the char under the cursor
• Fix 1000dl to delete the last char of the line
• Fix df<char>, cf<char>, dt<char>, and ct<char> to delete the char under the cursor after the movement
• Fix dF<char>, dT<char> not to delete the char under the cursor
• Fix cj to remain a single line
• Fix yy to allow to take a universal argument
• Fix J not to skip empty lines, and don't allow to concatenate the following ones
• Fix J and gJ to allow to take a universal argument, like 3J to join 3 lines
• Fix J not to add a space in between if the next line starts with a ')' not only when the current line ends with ')'
• Fix J in visual mode to join lines between pointers
• Fix D in visual mode to delete the whole lines between pointers
• Fix r to work in visual mode
• Fix r to allow to take a universal argument, like 2r<char>
• Fix the cursor position when s is pressed on the last char of the line
• Fix dG to delete to the end of the buffer instead to the begin
• Fix dM and dL to delete the line if the pointer is the end of the buffer after the movement
• Add gU and gu to change cases in normal mode
• ...and more, fix a lot of operations that move the cursor to the wrong position after they run

I also found strange behavior of e and E, but I decided to leave them not to make changes huge.