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 branch 'master' of github.com:pardom/ActiveAndroid
Fixes issue from Pull Request #175 with custom Id column name.

Unique Groups and Index Groups caused a conflict with allowing for a custom Id column name.

This was discovered in Pull Request #175.