add flatbuffers support and initial rewrite

Signed-off-by: Folling <mail@folling.io>

include/ikarus/models/entity.fbs

@@ -0,0 +1,26 @@
+include "value.fbs";
+include "property.fbs";
+include "blueprint.fbs";
+
+namespace Ikarus;
+
+table NamedValue {
+    name: string (key);
+    value: Ikarus.Value.Value;
+}
+
+table PropertyValue {
+    property_id: int64 (key);
+    data: Ikarus.Value.Data;
+}
+
+table Entity {
+    id: int64;
+    name: string;
+    description: string;
+    tags: [string];
+    values: [NamedValue];
+    property_values: [PropertyValue];
+}
+
+root_type Entity;