S3 bucket listing support and network code refactors.

* Adds support for listing all objects in an S3 bucket.
* Renames a bunch of network related classes (Download->Action)
* Net actions now have static constructors

logic/net/CacheDownload.cpp

@@ -8,7 +8,7 @@
 #include <logger/QsLog.h>
 
 CacheDownload::CacheDownload(QUrl url, MetaEntryPtr entry)
-	: Download(), md5sum(QCryptographicHash::Md5)
+	: NetAction(), md5sum(QCryptographicHash::Md5)
 {
 	m_url = url;
 	m_entry = entry;