Distinguish non LEAP provider and down provider.

I've set ProviderAPI to show its own toast depending on the exception
that getStringFromProvider issues. If the socket timeout reaches its
end, a toast different from when an IOException or a MalformedException
occur.
Shows certificate error message.

If a download didn't occurr due to an IOException, we assume it was for
an SSL error and notify the user telling him/her that LEAP provider is
not trusted.