update to version 1.5.0

* added REST server implementing OpenDHT proxy API
* tools: added simple Web client using the proxy server
* tools: allow dhtnode to run a proxy server
* tools: allow dhtnode to use any string as key
* InfoHash: added operator bool()
* minor performance improvement
* SockAddr: fix endianness issue
* net: fix incorrect reported address parsing
* minor memory leak fixes