LibVLC user may want to re-use this surface.

This reverts commit ec54269b.

This fixes inconsistent exception catching, and therefor fixes potential
uncaught exception while discovering/parsing, leading to std::terminate
being called

For reloads, like on regular app launch, we show notification only if
new media are parsed

This reverts commit fad767ac.

Load each content separately, to avoid wait before displaying the first
one

We keep 2 threads ready for reuse