maxym.kononets/modelHomework: realization Singleton and late static binding

realization Singleton and late static binding

maxkononets 3954c4b720 general commit		пре 5 година
Author.php	3954c4b720 general commit	пре 5 година
Book.php	3954c4b720 general commit	пре 5 година
DB.php	3954c4b720 general commit	пре 5 година
Model.php	3954c4b720 general commit	пре 5 година
User.php	3954c4b720 general commit	пре 5 година