Fix support of custom forms in Studio integration

TaCoKit Component-API has @GridLayout, which allows to define Properties Form.
Studio integration recognizes only Main and Advanced forms, but user may define some custom form too like @GridLayout(names = "MyForm")..

Following logic should be implemented:
1. If user defines Main form either explicitly (@GridLayout(names = FormType.MAIN)) or implicitly(GridLayout without any name), then custom form should be ignored.
2. If there is no Main form, but there is custom form, then all custom forms should be merged into Main form.