Move ThemeServiceProvider and AddonServiceProvider to CRUD

[tabacitu]

Right now all our addons have their own service providers, which extend an AutomaticServiceProvider that lives in each.freaking.package. While that has worked ok so far, because we were unsure whether we want to make changes to them (and we did), we haven't needed to make changes to them in a while. That means they're stable. Different... but stable.

So what I propose we do is create two ServiceProvider classes in CRUD, to hold the logic that is now in the AutomaticServiceProvider:

• ThemeServiceProvider
• AddonServiceProvider

Then each package's provider can just extend it.

Notes:

• not all AutomaticServiceProvider classes are identical; we have to spot the differences before we delete them from their respective packages; and make one provider that caters to all (or override just that one bit they need);
• ThemeServiceProvider and AddonServiceProvider are very similar; so they should share a lot of stuff using traits, or perhaps one extending the other;

[tabacitu]

Note: I've already done this for ThemeServiceProvider, because it wasn't very difficult, we had only 3 packages using it (ours) and they were identical.

Next up: Doing the same for AddonServiceProvider. But that'll take a lot more time because there ARE small but important differences between them in our packages. Postponing until we get more room to breathe.