Add &co escape

Am I missing any symbols that would still benefit from being escaped?
Adjust how properties function: Adjust within the property class file itself

Update dItems entirely, set empty TODO's for entity and inventory.
No more excuses for properties that don't adjust.
Allow health input in player -> show_boss_bar

Input like:
- adjust <player> show_boss_bar:Hello
- adjust <player> show_boss_bar:100|Hello
Allow m@ in item script materials

While it is better to load as a dItem than a dMaterial, the meta and
some existing scripts use m@... just let that slip by.
Allow constructing elements via el@

el@ wasn't a valid constructor, only el@val[...]
Now both work fine.
Allow offline player dInventories

The commit name describes the main point.
This also adds methods for future mechanisms and tags to access/edit
offline information.
Allow <p@player.location> to return the last location of offline players
Merge pull request #644 from mcmonkey4eva/master

Beginning of a large pull request