[O] M-RET and C-RET

[sindikat]

> You can use M-RET-may-split-line, to make it respect content in lists,
more or less. I would guess the reason that they are different is to be
able to always easily start a new heading. 

This is very helpful, thank you. But how to make it so M-RET will: 

1. not split line;
2. add new list item while on plain list;
AND
3. add new heading after content of the current heading? 

Maybe there should be a variable in addition to 'org-M-RET-may-split-line' 
such as 'org-M-RET-add-after-content'. 

Btw, i think it is bad to name an Emacs after keyboard combination, because 
it is ambiguous in case user remap M-RET. This is a minor issue, but still 
:)