Change item::material to return a material pointer directly.

Previously item::material returned only the material ident. That ident has been used to get the material_type object. Now this is already done by the get_material function.

Use material ident null instead of empty ident for is_null check. The
json file contains a material with ident "null" and some code also
relies on it.
Search for translated material name in game::list_items_match

Also made search for category and material case-insensitive.
Random character respects INITIAL_POINTS now
Let random char creation respect max stat/skill
Merge branch 'material-n' of https://github.com/BevapDin/Cataclysm-DDA into Bugfixes
Merge branch 'random_character_points_fix' of https://github.com/Wuzzy2/Cataclysm-DDA into Bugfixes