Some Fixes for HTML Docs Generated by LDoc (#60)

* LDoc: set min-height for "content" element
* LDoc: move generation script to .ldoc directory
* LDoc: add some output messages to gendoc.sh script
* LDoc: copy inventory image textures to reference dir instead of linking to remote files.
* LDoc: hack to compensate for "shields:" prefix being trimmed from item names
* Fix helmet_diamond & chestplate_crystal names in docstrings

shields/init.lua

@@ -1,5 +1,5 @@
 
---- Registered shields.
+--- 3D Armor Shields
 --
 --  @topic shields