Major plugin refactor and cleanup.

Switched to POCO library for unified platform/library interface.
Deprecated the external module API. It was creating more problems than solving.
Removed most built-in libraries in favor of system libraries for easier maintenance.
Cleaned and secured code with help from static analyzers.

vendor/CPR/include/cpr/verbose.h

@@ -0,0 +1,18 @@
+#ifndef CPR_VERBOSE_H_
+#define CPR_VERBOSE_H_
+
+namespace cpr {
+
+class Verbose {
+  public:
+    Verbose() = default;
+    // NOLINTNEXTLINE(google-explicit-constructor, hicpp-explicit-conversions)
+    Verbose(const bool verbose) : verbose{verbose} {}
+
+    bool verbose = true;
+};
+
+} // namespace cpr
+
+
+#endif /* CPR_VERBOSE_H_ */