Rewrite electricity-logger to use an sqlite3 database

include/electricity/server/database.hpp

@@ -0,0 +1,8 @@
+#include <string>
+#include <util/date.hpp>
+
+namespace Server::Database
+{
+    std::string GetDetailedJsonOf(Util::Date const & date);
+    std::string GetSummaryJsonOf(Util::Date const & startDate, Util::Date const & stopDate);
+}