Drop builtin command documentation

Drop all GetTerseDocumentation and GetFullDocumentation methods from
commands.  The command documentation is now in Help/command/*.rst files.

Source/cmFindProgramCommand.h

@@ -50,19 +50,10 @@ public:
    */
   virtual const char* GetName() const { return "find_program";}
 
-  /**
-   * Succinct documentation.
-   */
-  virtual const char* GetTerseDocumentation() const
-    {
-    return "Find an executable program.";
-    }
-
   cmTypeMacro(cmFindProgramCommand, cmFindBase);
 
 protected:
   std::string FindProgram(std::vector<std::string> names);
-  virtual void GenerateDocumentation();
 
 private:
   std::string FindAppBundle(std::vector<std::string> names);