MPA

When testing the dynamic loading it is hard to notice bugs because of the way the content is loaded.
Let's improve the loading so that we can clearly see if some behavior are bugs.

Currently:
When scrolling down, the new batch of content is loaded in place, meaing that it appears at the current viewed position (the new sounds appear at the same positionn as the old one)

Improved:

1. Add loader:
Let's add the spinning wheel at the bottom of the sound list when a new batch of soud is being loaded.

2. Load below existing content:
To not get confusing, the new content should always be loaded below the existing content.
This means that the items currently viewed are not chaging position when new content is loaded, the new content is loaded below the currently viewed files and is visible only when scrolling.

This is a pretty standard behavior, you could have a look at the Facebook timeline or Instagram ect if you need a precise model...

2. Load below existing content
this part done

1. Add loader
this part also done, please check it

It is fixed, but deactivating the sorting has introduced some bugs, which are reported in another task