Cleaning up the MoveLeft and MoveRight functions

[hugomg]

This PR continues the cleanup effort from #45.

• Add comments
• Consolidate MoveCharRight and MoveCharLeft
• Consolidate MoveBlockRight and MoveBlockLeft
• Stop using "silent" where we didn't need to
• Stop leaking the value of the default register
• Stop using the finicky functions with the "range" attribute -- use for everything.

I think everything is still working but I would appreciate if you could double check, specially the MoveBlockHorizontally. Some of those changes were not trivial and I'm not 100% sure that I was able to test all the corner cases.

[matze]

I think everything is still working but I would appreciate if you could double check

Looks good to me and works as expected. Do you plan to add more clean ups?

[hugomg]

For now the only thing I still want to do is reorder the functions so the two MoveVertically and the two MoveHorizontally functions appear next to each other. But I didn't include that commit in this PR in order to keep the diff easier to read. I could add it to this PR or to a new PR.

[matze]

As you prefer ;-)

[hugomg]

OK, I added that commit as part of this PR.

[matze]

Great thanks! :+1: