Expose InMemoryCacheAdapter

[steven-supersolid]

This is to make it possible to configure caching from index.js:

var InMemoryCacheAdapter = require('parse-server').InMemoryCacheAdapter;

var cacheAdapter = new InMemoryCacheAdapter({
            ttl: Number(process.env.PARSE_SERVER_CACHE_TTL)
        });

var api = new ParseServer({
    ...
    cacheAdapter: cacheAdapter
});

[steven-supersolid]

I also removed this unused import

[blacha]

Looks good to me

[TylerBrock]

Same here.