Documentation says the limit is 5, but it was really 10 (at least
since 2004).  But since MPD wants to promote using many small clients
idling around, and these clients consume only very few resources, it
seems reasonable to raise this limit's default value.

This fixes use-after-free bug in SimpleDatabase::Close(), accessing
the `root` object which was already freed by the `catch` block in
Open().

By having the Database on the stack first, we can avoid calling
Close() on the failed-to-open Database from Instance's destructor.

Closes #482

Destruct automatically, even if leaving the scope due to exception
being thrown.

The list of partitions is cleared automatically.

They will be stopped by ~EventThread() when the `Instance` is deleted.

Keep MPD's footprint small until playback is requested.

A Java object to send logs on the android side.

Eliminate yet another access to the global ConfigData instance.

Let MainOrThrow() forward it to mpd_main().

Deinitialize the logging library after the last exception handler,
because that one could still need it.

Use `AtScopeExit()` to ensure it's always called, even if an exception
was thrown.