Log loaded classes by SmackConfiguration
Reworked DiscoverInfo and DiscoverItems

- Change the return type from Iterator to List
- Remove the synchronized blocks
Cleanup SASLAuthentication

- Synchronized as method keyword
- Removed star import
Further improved logging in SmackConfiguration
Remove cache from DNSUtils

Caching of DNS RR should happen on the lowest possible layer, not within Smack:
- dnsjava does it's own caching
- resolving via the javax API should use the OS's caching (if any)

We don't need dozens layers of DNS RR caching.
Use gradle dynamic versioning for dnsjava
Return empty list instead of null in DNSUtil
Fixed NPE in FromMatchesFilter

in cases where a 'null' FromMatchesFilter was used and the processed
message would have a non-null 'from' attribute.

Thanks to sylvia for reporting this.
Add log to DNSUtil
Fix log message in SmackConfiguration

Those startup classes could be specified in other files besides
smack-config.xml
Add support for CustomSmackConfiguration class

with DISABLED_SMACK_CLASSES String[] option.
Fix SmackConfiguration disabledSmackClasses

contains() should ckeck against 'classToLoad' not 'name'.
Cleanup of pingMyServer() API

only throw NotConnectedException, otherwise return false. Before as
some sort of exception was always thrown in the error case.