jshell tool: detect paste so that multi-line constructs aren't processed until the end of the paste

Use JLine functionality to detect pastes, then process them as one block.

E.g.:


"Hello".toUpperCase()
       .length();

jshell will process the first line as a snippet (as semi-colons are optional) so we were mulling over whether there would be any way to make it easy to paste in multi-line code examples like this.

(Thanks Matthew and Alan))