Draft: reconstruct flash subs and commands

[sidey79]

• Please check if the PR fulfills these requirements

• Tests for the changes have been added / modified (needed for for bug fixes / features)
• commandref has been added / updated (needed for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

• Bugfix (please link issue)
• Feature enhancement
• Documentation update
• Unittest enhancement
• other

• What is the current behavior?
  (You can also link to an open issue here, if this describes the current behavior)

• What is the new behavior (if this is a feature change)?

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)

• Other information:

[codecov]

Codecov Report

❌ Patch coverage is 96.32893% with 25 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.68%. Comparing base (1980795) to head (382d9ae).
⚠️ Report is 18 commits behind head on master.

Files with missing lines	Patch %	Lines
lib/FHEM/Devices/SIGNALduino/SD_Firmware.pm	88.44%	23 Missing ⚠️
...M/Devices/SIGNALduino/SD_Firmware/01_sub_avrdude.t	99.48%	1 Missing ⚠️
...SIGNALduino/SD_Firmware/02_sub_availableFirmware.t	99.65%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1347      +/-   ##
==========================================
+ Coverage   89.17%   92.68%   +3.50%     
==========================================
  Files         151       63      -88     
  Lines       11052     4335    -6717     
  Branches     1717      319    -1398     
==========================================
- Hits         9856     4018    -5838     
+ Misses       1196      317     -879     

Flag	Coverage Δ
fhem-00_SIGNALduino-5.24	?
fhem-00_SIGNALduino-5.28	?
fhem-00_SIGNALduino-5.32	?
fhem-other_modules-5.24	?
fhem-other_modules-5.28	?
fhem-other_modules-5.32	?
perl-modules-5.24	92.47% <96.32%> (+0.63%)	⬆️
perl-modules-5.28	92.54% <96.32%> (+0.95%)	⬆️
perl-modules-5.32	92.61% <96.32%> (+0.69%)	⬆️

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