Fixed build errors and some crashes; some UI tweaks

Replaced Dropbox-iOS-SDK with DropboxSDK, and CrashlyticsFramwork with Crashlytics
Fixed a lot of the warnings
Refined the section index GUI when the theme is translucent, as I thought that it was disabled because the white background looked ugly (but left it off for now)

Fixed some UI bugs/crashes in Settings pertaining to controller skins, including:
GBA4iOS would crash if the GBAControllerSkinDownloadViewController was exited while downloads were still occurring, fixed by disabling "Done" until downloads complete
Moved "Add" new skins button up a level to GBASkinSelectionViewController for logical reasons, skin downloads are both portrait and landscape and should be downloaded as a whole, not in the GBAControllerSkinDetailViewController which one or the other

Fixes a bug with the status bar hiding when switching to the ROM tableview after a rotation (for example, going from the ROM tableview in portrait mode, starting a game, rotating the screen, and exiting back to the menu while still in landscape will cause the status bar to disappear permanently, even in portrait mode, until the emulation is resumed and put back in portrait).