Convert builtin help to reStructuredText source files

Run the convert-help.bash script to convert documentation:

 ./convert-help.bash "/path/to/CMake-build/bin"

Then remove it.

Help/command/include.rst

@@ -0,0 +1,25 @@
+include
+-------
+
+Load and run CMake code from a file or module.
+
+::
+
+  include(<file|module> [OPTIONAL] [RESULT_VARIABLE <VAR>]
+                        [NO_POLICY_SCOPE])
+
+Load and run CMake code from the file given.  Variable reads and
+writes access the scope of the caller (dynamic scoping).  If OPTIONAL
+is present, then no error is raised if the file does not exist.  If
+RESULT_VARIABLE is given the variable will be set to the full filename
+which has been included or NOTFOUND if it failed.
+
+If a module is specified instead of a file, the file with name
+<modulename>.cmake is searched first in CMAKE_MODULE_PATH, then in the
+CMake module directory.  There is one exception to this: if the file
+which calls include() is located itself in the CMake module directory,
+then first the CMake module directory is searched and
+CMAKE_MODULE_PATH afterwards.  See also policy CMP0017.
+
+See the cmake_policy() command documentation for discussion of the
+NO_POLICY_SCOPE option.