Imageloader optimization for old device

I updated the code to have a better scrolling in the Search list on my Android 5.0 of more 2 years old.
Scrolling was really bad in the search list with several Janks in Trace result.
Now it's OK with the UI, also OK with the CPU and memory.
I didn't change too much the code, mainly the parameters of 2 main recyclers and parameters of ImageLoader by adding disk cache, raising the thread priority, raising the thread pool, reducing the pixel coding and adding some final variables for JIT. There is more to do but with small changes I think we got a result.

If you can test it on your old device... :)