Unify base page structure - EditorPage

[G-Ambatte]

#1423 was an attempt to unify the underlying editor page for NewPage and EditPage. However the rest of the project moved on before the PR was completed.

This issue is to record the idea - unifying the underlying page structure so that functions do not need to be modified in multiple places - so that it is not lost with the closure of #1423.

My intention is to close #1423 and open a new PR with a smaller, sleeker set of changes, implementing a minimal combined EditorPage to be called by NewPage and EditPage, which can be merged further through later PRs.
I also intend to push UserPage through an underlying ListPage, which can be used for any future pages that need to list multiple brews.

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This issue is to track to the creation and progress of the EditorPage base page.