* Code modernization: subfolders
Modernize various code on subfolders client, network, script, threading, unittests, util
* empty function
* default constructor/destructor
* for range-based loops
* use emplace_back instead of push_back
* C++ STL header style
* Make connection.cpp readable in a pointed place + typo
- Add ability to explicitly reset NodeResolve state (useful for unittesting)
- Remove non-essential NodeResolve methods modifying state from INodeDefManager
- Add const qualifier to NodeDefManager and ContentFeatures serialize