Automatic migration support

I have added automatic migration support. It will be applied when manual migrations do not update database to the latest version. There are two ways of automatic migration:

* When new columns are added, unique and/or primary key columns are added and existing columns are not affected - it will add columns by altering existing table.

* When model has new unique and/or primary key column, or existing columns were affected it will rename existing table, create new table with updated schema and copy data from old table to the new one.

**Limitations:**

*Automatic migration does not support changing of column type, IncompatibleColumnTypesException will be thrown.*

*Automatic migration cannot detect renaming of the table (new table will be created and no data from old column will be copied)*