associate with *.mdown, *.markdown; make it finally 1.0 with command

`mvn -Dtycho.mode=maven
org.eclipse.tycho:tycho-versions-plugin:set-version
-DnewVersion=1.0.0-SNAPSHOT`

This is not finished change as currently build fails on site module: 

	[ERROR] Failed to execute goal org.eclipse.tycho:tycho-p2-repository-plugin:0.18.1:assemble-repository (default-assemble-repository)
	 on project markdown.editor.site: No content specified for p2 repository -> [Help 1]
	[ERROR]

It is 11pm, and I absolutely don't see why it cannot build (while it can on similar projects)