Chore (keydown): improve behaviour of getOutOfList

[e11sy]

Problem

1. After splitting of the list on first item we get two lists. One of them is empty (even no item, so just empty wrapper with paddings is left)
2. After pressing backspace at start of the first item, we should convert first item of the list to the paragraph

Solution

• Added removeBlock parameter to the getOutOfList() method, that represents condition, when List block should be removed after getting out
• Added getOutOfListFromFirstItem() method, that unshifts child items of the first element, and calls getOutOfList with right conditions