R1:21efc7cb649f

Show all configuration defaults when editing configuration

Summary: Show the value for all loaded configuration sources.

Test Plan:
{F28469}

{F28470}

{F28471}

Reviewers: btrahan, codeblock

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2255

Differential Revision: https://secure.phabricator.com/D4312