Lataa NZBGet 23.0

What's Changed
- Features:- Extension Manager #76;- The new nzbget extension system, which makes it easy to download/update/delete
extensions with backward compatibility with the old system;
- extensions master list;
- changed:- RPC request "configtemplates" - no longer returns script templates, but only the config template;

- added:- new RPC requests:- "loadextensions" - loads all extensions from {ScriptDIR} and returns an array of structures in JSON/XML formats;
- "updateextension" - downloads by url and name and installs the extension. Returns 'true' or error response in JSON/XML formats;
- "deleteextension" - deletes extension by name. Returns 'true' or error response in JSON/XML formats;
- "downloadextension" - downloads by url and installs the extension. Returns 'true' or error response in JSON/XML formats;
- "testextension" - tries to find the right executor program for the extension, e.g. Python.
Returns 'true' or error response in JSON/XML formats;

- "EXTENSION MANAGER" section in webui to download/delete/update extensions;
- Boost.Json library to work with JSON;
- more unit tests;

- refactored:- replaced raw pointers with smart pointers and const refs where possible for memory safty reasons;

- removed:- testdata_FILES from Makefile.am;
- EMail and Logger scripts;

- Docker support #55;
- Synology support (spk) #72;
- QNAP support #158;
- aarch64 mipseb mipsel ppc6xx ppc500 architectures to linux build #61 #146;
- article read chunk size #52;- Added ArticleReadChunkSize config option which allows to adjust
the buffer size for customization on different platforms, which can lead to increased performance;

- increased the number of default connections to 8 #54;
- automatic search for a suitable interpreter on POSIX #74;
- certificate verification levels #150;- levels:- None: NO certificate signing check, NO certificate hostname check;
- Minimal: certificate signing check, NO certificate hostname check;
- Strict: certificate signing check, certificate hostname check;

- tested on a mock nzbget NNTP nserv server with self-signed certificate and got expected results:- "Strict" -> test failed;
- "Minimal" -> test failed;
- "None" -> test passed";

- Bug fixies:- possible memory corruption #148;

- For developers:- fixed unit tests (Windows only for now) and started migration to CMake #64;- We are going to completely migrate to CMake as a more universal one for cross-platform development and drop autotools and MSBuild;

- using libxml2 on Windows and vcpkg package manager to install dependencies #70;- libxml2 library is now used on Windows to work with xml in the same way we already do on Linux and macOS;
- removed platform-dependent code for working with xml on Windows;