Add converter for number to hex

[krogenth]

For some items, it would be beneficial to display values as their hexadecimal counterparts. This is primarily for the MapEntries view, where the entry ID is the map ID, based on the map filename(though there is likely another value within each file that specifies their ID).

Tasks:

• create convert for number to hex string and back to number
• add use of converter to MapEntries Map ID textbox