Changed Blob Cache to use an IBlobCacheProvider

[PureWeen]

Changed Splat registrations to use an IBlobCacheProvider so how the cache is created can be reused and tapped into more easily. Static caches retain current behavior. Also added some static helpers to BlobCache

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
Feature

What is the current behavior? (You can also link to an open issue here)
How Blob Caches are constructed isn't really exposed at all to a user. If I don't want to to use the static helpers I don't have a great way to reuse how Akavache news up the Blob Caches.
#342

What is the new behavior (if this is a feature change)?

How BlobCaches are created currently can't be reused very easily and overall I think this leads to some difficulty for new users with implementing the life cycle correctly in something like mobile apps. I set it up to register two different types of IBlobCacheProviders.

Does this PR introduce a breaking change?
It shouldn't. If someone was registering on top of the current Splat registrations (i.e. "UserAccount") those should still work just fine

Please check if the PR fulfills these requirements

• The commit follows our guidelines: https://github.com/Akavache/Akavache/blob/master/CONTRIBUTING.md
• [X ] Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Other information:
If how I did this is something that is appealing and gets merged I'll add some additional docs around these.

My initial thought was just to add an additional Splat registration with Func's but then I decided to go the provider route
Here is that branch in case anyone is interested
https://github.com/PureWeen/Akavache/tree/added_splat_registration_to_new_up_caches

[ghuntley]

Parking this one & not including in the release that's going out in a couple moments. Don't have time to properly consider the impact. Thanks @PureWeen as always.

[Im-PJ]

Will this be merged? I was using static BlobCache everywhere in XF and I think I'm doing wrong after reading this.

[anaisbetts]

What if instead we just extracted this logic out into a method:

fs.CreateRecursive(fs.GetDefaultLocalMachineCacheDirectory()).

and made it so that you got the path to this? createDefaultLocationForCache(BlobCacheType.Secure) or something. That way people can easily recreate BlobCache.*, without the AbstractFactoryBeanProvider :)