REPL: Multiple script fragment support

Add support for multiple script fragments in the REPL.

Signed-off-by: Pekka Enberg <penberg@iki.fi>
InteractiveTest: Application expressions

Add test cases for application expressions that are supported by Fjord
now that we can evaluate more than one expression in the REPL.

Signed-off-by: Pekka Enberg <penberg@iki.fi>