enter on elements doesnt exit it

[jdonszelmann]

when pressing enter in for example a codeblock, you stay in the codeblock and it will be enlarged. however sometimes this is not what you want. you actually want a new line below. in many cases this is trivial because you just click below the codeblock. it is however a problem when the codeblock is the last line in a post because then there is no line below to click on.

solution: add a control-enter or shift-enter to exit block and newline

[RobbinBaauw]

Closing in favor of #190