Added support for custom wiki sidebar using _sidebar.md in the wiki root. If _sidebar.md exists it will be parsed and rendered otherwise the default sidebar file list  will display

deleted _sidebar_custom.html.haml and modified _sidebar.html.haml to check for sidebar_page and render it or the default wiki page list. Also removed white space.

fix indent in show.html.haml

restore newline at end of ile

Add a newline at the end of changelogs/custom_wiki_sidebar.yml