Noissue - Update docs to describe include files metadata override

docs/content/includes.md

Index: docs/content/includes.md
===================================================================
--- a/docs/content/includes.md
+++ b/docs/content/includes.md
@@ -2,9 +2,12 @@
 
 The following tag inserts an include file into the page (can be in a different
 format):
 
     <? include foo ?>
 
 Include files should be placed into the `includes` directory of the repository.
 In the case above the contents of `includes/foo.md` or `includes/foo.tmpl` will
-be inserted (whichever is present).
+be inserted (whichever is present).
+
+Also, page front matter (metadata defined at the top of the file) will

[Vasily Kuznetsov, 2018/03/01 15:41:21]

Maybe better to formulate this as something like "the metadata variables from
the include file will be added to the page metadata (with the metadata variables
from the include having priority)"? What do you think?

[Jon Sonesen, 2018/03/02 00:58:01]

Yeah thats much better, thanks. This means that an include can change the
template of a page correct? if so perhaps this should also be pointed out.

[Jon Sonesen, 2018/03/02 01:10:14]

basically add to yours, "this means that a include file is capable of things
like overriding a page's default template."?

+be overridden by the included file.