rest-api-templates/asterisk_processor - replace http line breaks with line feed

Including line breaks (<br>, <br/>, <br />) in certain parts of the rest-api
json definition (e.g. summary, notes) displays them correctly in swagger.
However, when the field gets converted to the wiki format those breaks get
escaped and show up in the text as the actual string literal "<br>" etc...

This patch makes it so when converting to the wiki format it replaces all line
break values (<br>, etc...) with line feeds ('\n').

Change-Id: Ie1c9faa0d1c5d622804cc0a21ce769095b08aa3d