Add method in Table annotation for set column Id name.
This fixes Issue #83

example:
@Table(name = "Items", id = BaseColumns._ID)
public class Item extends Model {...}

Conflicts:
	src/com/activeandroid/Model.java
	src/com/activeandroid/TableInfo.java
Merge pull request #175 from hube/add_id_annotation

Add method in Table annotation to set column Id name.