Remove menu_title when not needed

systems/arXMLiv.md

 ---
 layout: system
-menu_title: arXMLiv  
 title: arXMLiv
 start: 2006
 pillar: semantization

systems/cpoint.md

 ---
 layout: system
-menu_title: CPoint
 title: CPoint
 teaser: Adding a semantic layer to MS PowerPoint.
 start: 2001-07

systems/jomdoc.md

 ---
 layout: system
-menu_title: JOMDoc
 title: JOMDoc
 teaser: A Java API for OMDoc documents.
 start: 2007-09

systems/krextor.md

 ---
 layout: system
-menu_title: Krextor
 title: Krextor
 start: 2008-02
 end: 2010-09

systems/mathhub.md

 ---
 layout: system
-menu_title: MathHub
 title: MathHub
 teaser: A portal for active mathematical documents and an archive for flexiformal mathematics.
 start: 2008-08

systems/openmathmap.md

 ---
 layout: system
-menu_title: OpenMathMap
 title: OpenMathMap
 teaser: A Map of Mathematics
 start: 2013-06

systems/sally.md

 ---
 layout: system
-menu_title: Semantic Alliance
 title: Semantic Alliance
 teaser: A framework for mashing up semantic services into desktop applications.
 repository: https://github.com/KWARC/Sally

teaching/ai1.md

@@ -2,7 +2,6 @@
 layout: course
 instructor: mkohlhase
 title: Künstliche Intelligenz I
-menu_title: Künstliche Intelligenz I
 taught: WS16
 ---
 Diese Vorlesung beschäftigt sich mit den Grundlagen der Künstlichen Intelligenz (KI),

teaching/ai2.md

@@ -2,7 +2,6 @@
 layout: course
 instructor: mkohlhase
 title: Künstliche Intelligenz II
-menu_title: Künstliche Intelligenz II
 taught: SS16/17
 ---