added new config option to enable coloring item levels relative to ch…

[kevinfealey]

This PR is to address issue 168.

This PR adds a new option to both bag and bank configuration to enable "Dynamic color" for item levels based on the item's ilvl relative to the character's average item level.

When enabled, the following logic is used to determine the item's color.

• item level is above or equal to average item level = orange
• item level is 10 or less lower than average item level = purple
• item level is 1-15 lower than average item level = blue
• item is 16-20 lower than average item level = green
• item is more than 20 lower than average item level = yellow

The ranges and colors are somewhat arbitrary, but are intended to provide "at a glace" usefulness of gear in bags and bank. For example, I generally would not equip gear that is not purple or orange, except in specialized situations (e.g. timewalking).

This functionality could be extended to allow user's to configure item level ranges and colors in the future.

Note that this PR only addresses retail. This implementation was tested in retail 10.2.5 (today, on February 20, 2024). Classic configurations were not created or tested, but it should be trivial to add them by simply modifying the corresponding bags.lua in the same way this bags.lua was modified.