Fix imagerotate and move loadFromBase64() one up

`imagerotate()` with third parameter being -1 does not seem to work in PHP 5.5

`loadFromBase64()` one up, so debug-logs aren't spammed (as much) with urlencoded base64-data from `loadFromFile()` debug output.

Not sure whether the order in `OC_Image->load()` has to be the way it is now (base64-like file-paths?), but doing some short tests didn't seem like it.