* net: don't import std namespace
This file is about to be broken up into chunks and moved around. Drop the
namespace now rather than requiring other files to use it.
* net: remove unused set
* net: use the exposed GetNodeSignals() rather than g_signals directly
* net: make Ban/Unban/ClearBan functionality consistent
- Ban/Unban/ClearBan call uiInterface.BannedListChanged() as necessary
- Ban/Unban/ClearBan sync to disk if the operation is user-invoked
- Mark node for disconnection automatically when banning
- Lock cs_vNodes while setting disconnected
- Don't spin in a tight loop while setting disconnected
* net: No need to export DumpBanlist
