Fix Juniper shell delimitation recognition

Recognize the shell prompt on Juniper independently on last newline (which caused errors / hangs when the output from a command was empty).
Recognize the shell prompt on Juniper based on the "[^\s]+> " regexp.
Add escaping of "<something>" in TextCommand out

Escap strings that might be misinterptered as HTML tags in the output of TextCommand when default decorator (= <pre>%s</pre>) is used.