cpp console example app leaks memory

[oschonrock]

if you run the example app code with address sanatizer it shows that it leaks memory.

==451983==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 256 byte(s) in 1 object(s) allocated from:
    #0 0x7fdb7d4f8f27 in operator new(unsigned long) ../../../../src/libsanitizer/asan/asan_new_delete.cpp:99
    #1 0x7fdb7d3bbdd0 in sql::mariadb::SelectResultSet::create(sql::mariadb::Results*, sql::mariadb::Protocol*, sql::mariadb::capi::st_mysql*, bool) /home/buildbot/src/src/SelectResultSet.cpp:79

The issue is the result sets, eg this:

        sql::ResultSet *res = stmnt->executeQuery("select * from tasks");

needs to be wrapped in a unique_ptr to ensure it gets cleaned up at end of scope:

    std::unique_ptr<sql::ResultSet> res(stmnt->executeQuery("select * from tasks"));

This applies to every result_set in the example app. ie every time stmnt->execute*() is called