implement crypto

Signed-off-by: zyphlar <zyphlar@gmail.com>

libs/platform/platform.hpp

@@ -271,6 +271,9 @@ public:
   /// @return JSON-encoded list of urls if metaserver is unreachable
   std::string DefaultUrlsJSON() const;
 
+  /// @return default location sharing server URL
+  std::string LocationSharingServerUrl() const;
+
   bool IsTablet() const { return m_isTablet; }
 
   /// @return information about kinds of memory which are relevant for a platform.