Restructure folder layout for data storage and migrate existing data

[TheStonedTurtle]

Closes #10

The plugin will automatically try to migrate data to the new format when logging in. This logic should be removed in a future release once enough time has passed for a majority of the users to have triggered the automatic migration.

The folder structure for storing data inside ~/.runelite/loots has been updated as follows:

1) Changed folder name to use login username and not in-game display name. This will fix data loss/migration issues when changing names. 2) Separated record into their own folders by LootRecordType. This will fix issues where names collide for different record types, such as an NPC that can be killed and pick-pocketed.

Example Directory Tree

.runelite/
....
├── logs/
├── loots/
├   ├── *name*/
├      ├── event/
├      ├── npc/
├      ├── pickpocket/
├      ├── player/
├      └── unknown/
├── plugins/
....