Reduce the classpath lookups on misses

[pmlopes]

When resolving resources from the classpath, vert.x needs to make use of class loaders. This can be an expensive task. When a resource exists, it gets extracted to the cache and any further resolution is just a simple file system access.

However if there are misses, they always go over the classpath. ~To reduce the number of classpath scans, the resolver should make use of a inverted bloom filter. On each miss the miss is added to the filter. Given that the filter can return possible false negatives the consistency of the valid cases is guaranteed and we may end doing a few redundant checks which already is a good improvement.~