update readme

README.md

@@ -62,7 +62,7 @@ Currently, main application sources located at `src/app` folder, written by foll
 * At this moment, all constants named with uppercase, const everything that not mutable
 * `#include` application `.hpp` files in `.cpp`. For system libraries, use headers only. Do not place system dependencies in `.cpp`
 * App interact SQLite database, where table name match related class namespace, it may contain optional feature postfix (separated with double line)
-* Database table fields must contain only members of their class (e.g. private and public variable values) and may include primary keys to their parent class (tables) according to the namespace hierarchy
+* App class tables in database wanted to store user data between app sessions and must contain only fields that related to this class (e.g. private and public variable values); also may contain primary key fields, to their parent (table) according to the namespace hierarchy
 
 ### Environment