Add formatting of Lambdas.

This adds formatting of lambdas. If a lambda contains a newline
before the closing } it will be rendered on multiple lines. Otherwise
an attempt is made to render it in place (compact form). If the compact
form does not fit on the remainder of the line the lambda is rendered
using non compact form.
Make 'unless' format the same way as 'if'

The unless statement was not marked as being a BLOCK expression and
did not get the extra linebreak.
(497) Fixes formatting of selection inserts garbage. closes #497

The problem was that verbatim text parts of interpolated strings
were directly emitting the text without checking if it was part
of the current selection.
Merge branch 'dev' of git@github.com:cloudsmith/geppetto.git into dev