[MQTT] User must know if connected or not

[atrovato]

Fixes #1016

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Description of change

Display connection status on setup page.

[codecov]

Codecov Report

Merging #1349 (fcea130) into master (b6ab1c0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1349   +/-   ##
=======================================
  Coverage   96.54%   96.54%           
=======================================
  Files         613      613           
  Lines        8735     8735           
=======================================
  Hits         8433     8433           
  Misses        302      302           

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[Pierre-Gilles]

Works fine on my side!

[relativeci]

Job #155: Bundle Size — 6.67MB (+0.01%).

a5c95dc vs b6ab1c0

Changed metrics (2/8)

Metric	Current	Baseline
Initial JS	2.86MB(+0.03%)	2.86MB
Cache Invalidation	42.72%	0%

Changed assets by type (1/7)

	Current	Baseline
JS	4.76MB (+0.02%)	4.76MB

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View Job #155 report on app.relative-ci.com