Implemented dictionary functions

[functionaldude]

I'm currently developing an app, where I use a separate cache for debug information. This cache only holds debug information, if the app crashes the contents of the cache is uploaded to a backend server for analysis. Currently there is no other way to iterate over the contents of the cache.

[aschuch]

Please take a look at my current draft of AwesomeCache 3.0 (#56), is the new allObjects what you are looking for?

[functionaldude]

No, that doesn't work for me, because I need to upload the whole key-value pair. allObjects returns only the values. It is possible to use allObjects with a workaround, by generating a random key. Using that I could insert the original key and value as a tuple in the cache but as far as I know AwesomeCache doesn't support tuples as value.
The best solution would be a function that returns a snapshot of the cache as a NSDictionary.

[functionaldude]

I implemented 3 dictionary functions. asDictionary() returns the whole cache content, dictionaryWithValuesForKeys returns either keys with nils where the object is not present anymore (keysForNullableObjects) or no keys at all for nil safe calls (keysForObjects).

You can get a collection of the values (as discussed in #59) by calling asDictionary().values.