refactor data structure, scope, and security

• introduced test cases (#13)
• Created /{scope}/{key} where scope is a preconfigured thing that is in application.properties. (#12)
• Changed value to a clob. (#12)

If upgrading from version 2.x to 3.x and are already using an oracle database, need to run the following script. Adds a temporary column named temp that is a clob. Copies values over. Deletes old column. Renames new column as value.

alter table key_value add (temp clob);
update key_value set temp = value;
alter table key_value drop column value;
alter table key_value rename column temp to value;