[Util] Moved some files to util/network/.

The moved files are:
customcookiejar.*
customnetworkreply.*
socketerrorstrings.*
Merge branch 'master' of github.com:0xd34df00d/leechcraft
[Util] Moved NetworkDiskCache here from Core.
[Blasq] Use QtNetwork.
[Blasq] Added caching to the QML widget, fixes #1203.