Profile through sysprof

Start using some decent profiling to understand what's going on in the jobs.

@jfft you're going to like this ;)

I pushed this because I had this pending for quite some time back, but also to start proper research into #78 (closed). So far, the marks show that some of the initial jobs get stuck (likely due to some locking...), and this somehow freezes everything:

Some things missing:

• Provide a message, very useful for things like pages, etc.
• More granular requests