Fix cursor position after calling an each-based command, when possible

Hello :),

This is a small fix that attempt to get the cursor bask where it was after executing a command.

It works by checking if the number of lines hasn't changed and if so assume that the cursor can be set to its previous location.

Example without the fix (| marks the cursor position)

  - foo
  - bar|
   - baz

Calling ltrim will result in:

- foo
- bar
- baz|

But with the fix it will be:

- foo
- bar|
- baz

This is especially useful when calling rtrim on a big file (to quickly get rid of some auto-indent on lines left blank), as without the fix it moves the cursor to the end of the file which is not convenient.