Handle DPS scaling for weapons

[dmorcellet]

• standard weapons
• new legendary weapons
• old legendary weapons if possible

[dmorcellet]

Added DPS tables on all items. Checked that the computed DPS is equal to the on in the DAT files (for the default item level).

[dmorcellet]

Disabled item scaling for legendary items/weapons (old and new).

[dmorcellet]

Still TODO:

• fix the default item level in items.xml - sometimes it is 1 while scaling starts at 50+. Note that the DPS in the file matches the current item level in the file. If we change the default item level, then the DPS will be wrong.

[dmorcellet]

Item levels fixed (only for non legendary items). DPS updated accordingly. DPS value was not removed from items.xml

[dmorcellet]

Seems that all cases of item level fixes are for items with default item level=1 (assuming non legendary items).