Let addon manage the GUI's position (and size) instead of relying on the client's layout cache

[rdw-software]

Benefits:

• Allows uniform window position for all characters
• No accidental resets if the addon is deactivated or crashed for some reason
• Can still allow for different settings by using the AceDB profile
• Could use libwindow-1-1

Roadmap:

• Extend saved variables scheme to accommodate the layout cache (might need rework to add proper migration routine that works with AceDB)
• Save position continuously
• Restore position on login
• Change reset to also use those settings