Entry changes

I went to work on the API, I noticed that in `Entry` there was a place where the variable `notes` was used but it was never declared. So I went in, fixed that, and made some other changes in the class.  The diff looks like a mess, but the main points of the change are:

* Removed some of the excess constructors that I felt were unnecessary
* Changed `label` to `notes` to conform with what we talked about
* Made a copy of the date before returning it in `getDate()`
* Add `apiSave()` and `apiDelete()` methods that will call into the `ApiInterface`, as this seems like better style to me than calling directly into the `ApiInterface` from an activity. If anyone thinks otherwise, please comment.