ENH: Improve ctest_* command documentation

This corrects the terse documentation and adds detail to the full
documentation of some commands.  It also normalizes the layout of the
documentation string endings to make adding lines easier.

Source/CTest/cmCTestCoverageCommand.h

@@ -51,7 +51,7 @@ public:
    */
   virtual const char* GetTerseDocumentation()
     {
-    return "Tests the repository.";
+    return "Collect coverage tool results.";
     }
 
   /**
@@ -63,7 +63,8 @@ public:
       "  ctest_coverage([BUILD build_dir] [RETURN_VALUE res])\n"
       "Perform the coverage of the given build directory and stores results "
       "in Coverage.xml. The second argument is a variable that will hold "
-      "value.";
+      "value."
+      ;
     }
 
   cmTypeMacro(cmCTestCoverageCommand, cmCTestHandlerCommand);