VideoCommon: remove unused stats
Statistics: Reformat stats string
Fix dragging and dropping savestates in the render window
Fix ISO Directory extraction.
DiscIO: Fix extra tabs in the banner loader headers
DiscIO: Centralize the banner pointer and validity boolean into IBannerLoader

These are both used within the banner loaders, and IsValid is exactly the
same. So this makes sense.
Merge pull request #540 from lioncash/banner

Centralize some common banner loader class members.
Merge pull request #452 from degasus/stats

Video statistics update
Merge pull request #539 from jordan-woyak/fix-extract-directory

Fix ISO Directory extraction.
Merge pull request #538 from lioncash/savestate-dragdrop

Fix dragging and dropping savestates in the render window
Get rid of a few delete[] calls in sdio_slot0.cpp
Merge pull request #541 from lioncash/sdio

Get rid of a few delete[] calls in WII_IPC_HLE_Device_sdio_slot0.cpp
Add Change Disc option to the right-click menu in the game list. For issue 7411.