fixed some clippy warnings

Fades are broken, and I don't know why :(

Whoops. This doesn't become apparent with one channel (which is what
I was testing on), but when you use a stereo device, you hear obvious
desync.

Changes:
- Unloading now works, so deleting commands has the desired effect
- Sinks can now be removed from the Magister
- Load now stores its path as an actual PathBuf
- Stop/Unpause/Pause/Start functionality that is non-confusing
- Instead of having some odd "cue pointer", we now have a Reorder
  menu action
- Enable Fallthru menu action
- Cues are now numbers only
- Text was updated to better reflect the current state, with some
  nifty Live/Blind verbiage

We're ticking stuff off from issue #1!

itshappening.gif

Our spoolers now use only 20% CPU (on my machine) instead of like 198%
(due to spinwait). Yay!

Woo, work is getting done! (Sort of.)

It now just redraws. But intelligently!
Also, I just realised I forgot to commit src/cues.rs. Whoops.
That's next on my "to redo" list, so no biggie.

It looks so nice now! Yay.

This is item one on issue #1. Progress!

- Database is now a thing of the past. Phew!
- Everything is commands now.
- Chains are a new addition. What are they for? You'll see later!
- Identifiers now make sense, with nice autocompletes.
- Much more!

This commit gets rid of the last commit's crappy Action system, and
the terrible ReadableContext/WritableContext thing. Eugh. Now, the backend
acts more like a server, fielding Messages that the frontend sends it.
The frontend doesn't ever actually get to touch the commands themselves
(vastly simplifying things) - it gets CommandDescriptors that do the same job.

This implementation sucks and is only enough to execute a few commands to
show that it works. Don't use this!

This commit introduces the beginning of a system for keeping track of
commands. It's not done yet, and has embarrassing bugs (1.9 seconds? Sure,
that's just 1 second!)

- The backend now uses a MIO-based event loop. This is how fades work:
  the vol command just registers a timeout with MIO.
- UI errors are now a thing - these are errors that aren't generated
  by the command, but come as a result of not being able to translate
  the typed string in an Entry to the required type (u64, f32....).
  It's better than our old "ignore it completely" behaviour, and alerts
  the user of potential typos.

More bounded_spsc_queue. All the bounded_spsc_queue.

It plays audio now! Hooray! \o/

Changes:
- Command line code doesn't make me want to kill myself

(UI improvements, at the cost of crappy unorganised code)

This is the worst code I've committed in a while. Don't worry,
I won't merge it until it's better.

We needed something better than just text for a command line.
Tons of generics were the obvious solution.

(I'll explain what I'm doing later.)

New changes:
- We now have a pretty GTK+ UI. Woo, glade!
- Databases. Databases everywhere. (We now have a formal method
  for describing different types of stuff - it's great, look in
  state.rs for the juicy details)
- The program is split into a frontend UI thread and backend.
  This results in having a ReadableContext for the UI to play with,
  and a WritableContext in the backend for commands to operate on.
- Probably other stuff.

Changes that I haven't talked about in earlier commits:
- Everything uses commands. This works out well, because then cues
  just become lists of commands run in order.
- There's a nice parser. Trust me, it's VERY nice. (It took a day
  to write, so I hope it's nice.)

We now have all the commands implemented, but OMG THE COPYPASTA.
Seriously.
StartCommand is literally a copypaste of StopCommand.
This madness needs to stop.