Improve the form for adding new News

[ahnwarez]

When users register to gardenz, they select their preferred gardenz from a drop-down list, including admins and this does not make sense, because admins should be able to manage any garden they want.

The News page component in client/views/admin/News/AddNews/AddNews.jsx calls a helper function called addNews that reads the gardenId from the user object from global state. Instead of reading it form global state, we're going to add a drop-down list in the client/subcomponents/News/NewsForm/NewsForm.jsx to show all gardens and let the administrator select a garden.

Basically we want update that form so that admins write the title, content, upload photos for a specific garden.

• Add a drop-down list to the form (admin must select a garden from the list as a validation rule) #75
• Make the necessary changes in client/views/admin/News/AddNews/addNewsHelper.js to accept the gardenId as a parameter and not reading it from global state.
• Write tests for helpers, components, etc