Feature/93 improve backward compatibility to legacy md

[redcatbear]

@kaklakariada: I know, this is a large change. Sorry for this. Please review it anyway.

I am pretty sure it have importing and tracing the legacy format covered to a point where we can use it in production.

[codecov]

Codecov Report

Merging #100 into develop will increase coverage by 0.02%.
The diff coverage is 94.97%.

@@             Coverage Diff              @@
##             develop    #100      +/-   ##
============================================
+ Coverage      92.18%   92.2%   +0.02%     
- Complexity       672     716      +44     
============================================
  Files             76      79       +3     
  Lines           1842    1975     +133     
  Branches         154     169      +15     
============================================
+ Hits            1698    1821     +123     
- Misses           112     121       +9     
- Partials          32      33       +1

Impacted Files	Coverage Δ	Complexity Δ
...in/java/org/itsallcode/openfasttrace/Reporter.java	100% <ø> (ø)	1 <0> (ø)	⬇️
...llcode/openfasttrace/core/SpecificationItemId.java	93.61% <ø> (ø)	29 <0> (ø)	⬇️
...ode/openfasttrace/importer/markdown/MdPattern.java	92.3% <100%> (+1.39%)	3 <0> (ø)	⬇️
.../org/itsallcode/openfasttrace/core/ItemStatus.java	100% <100%> (ø)	5 <5> (?)
...enfasttrace/importer/SpecificationListBuilder.java	96.82% <100%> (+1.08%)	24 <12> (+8)	⬆️
...asttrace/core/xml/tree/CallbackContentHandler.java	86.27% <100%> (ø)	17 <0> (ø)	⬇️
...sallcode/openfasttrace/core/SpecificationItem.java	100% <100%> (+1.48%)	64 <3> (+10)	⬆️
...ode/openfasttrace/cli/commands/ConvertCommand.java	100% <100%> (ø)	4 <0> (ø)	⬇️
...code/openfasttrace/importer/MultiFileImporter.java	91.48% <100%> (ø)	18 <2> (ø)	⬇️
...llcode/openfasttrace/importer/ImporterService.java	100% <100%> (ø)	5 <2> (+1)	⬆️
... and 15 more

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