Boss level pull request

[urbanfog]

I looked through the code again tonight and made a few tweaks.

In summary, the changes are:

1. Flutter adding some iOS files. Not sure if these should be in git or not. I suspect it's because I've set myself up to develop and test on iOS and you haven't (e.g. cocoapods file is an iOS packages thing)
2. Split code into different files for the screens and 1 for your 'CounterStorage' class. I think there is still some clean-up /refactoring here because we are missing functionality like goal.save
3. Tweaked success screen styling and brought across the goal to remind the person. Also added a larger button as an alternate design idea.
4. Changed first page initState to pull the existing goal into a variable instead of auto setting it to the text that appears in the text field.
5. Misc changes.