Trailing newlines in variables prevent service startup

Bug/Issue

A trailing newline in job variables (at least, probably also service variables) will cause the generated service manifest to be invalid.

There is probably also an issue with newlines anywhere in the variable value, which is why we also filter out file-type variables. We should support passing variables with newlines.

What was the problem?

Newlines in variables cause an error in cf push of services:

yaml: line 44: did not find expected key