Fixes part of #16 and #44: Implementation of ProfileChooserFragment

[jamesxu0]

Explanation

Fixes part of #16 and #44: Implementation of ProfileChooserFragment. It also introduces ProfileTestHelper to help other test cases initialize admin and user profiles. Note the base branch is not develop but refers to PR #269.

Checklist

• The PR title starts with "Fix #bugnum: ", followed by a short, clear summary of the changes. (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
• The PR explanation includes the words "Fixes #bugnum: ..." (or "Fixes part of #bugnum" if the PR only partially fixes an issue).
• The PR follows the style guide.
• The PR does not contain any unnecessary auto-generated code from Android Studio.
• The PR is made from a branch that's not called "develop".
• The PR is made from a branch that is up-to-date with "develop".
• The PR's branch is based on "develop" and not on any other branch.
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[jamesxu0]

@BenHenning @rt4914 PTAL. I addressed all comments and fixed the test case.

[rt4914]

One test case issue which needs nit change.

[BenHenning]

Thanks @jamesxu0. This LGTM except the bit about changing the activity's children within a child. If that's going to go away in a subsequent PR, please feel free to ignore. If not, please fix here & re-assign to me if you think it's necessary. Otherwise, feel free to merge this in once comments are resolved.