Add manuel linking to ViewModel-like views

[smaugho]

Right now ViewModels are linked automatically by DecleX, but some times it could be useful (and informative) to link manually the ViewModel and the view, in the simple possible way.

A simple way to do this, is to make the populate methods or any view-linking (@click or similar annotation) to create a "linking" method, this will be used only in the "@export" behavior.

you can link the view model then to the view through methods, or assigns..

viewModel.linkGetUserName(R.id.userName);
viewModel.linkSomePopulatorMethodOrProperty(R.id.someId);

DecleX automatically could do this, but when the programmer do it, then it is not used the one done by DecleX.