Validate and add configurability for Jira issue link types; bug fixes

[JasperCraeghs]

• Support link type Blocks, configured by Atlassian for Jira Cloud.
• Add input argument [-L [LINKS ...]] to override the default configuration of Jira issue link types to take into account for TaskJuggler's depends keyword
• Validate existence of the aforementioned the configuration of Jira issue link types by retrieving all issue link types from the Jira instance
• Fix a rare and old bug that occurred when a task depends on two tasks with estimate of 0m successively, causing KeyError in if not id_to_task_map[identifier].is_resolved:
• Fix duplicate tasks for depends, resulting in an error by TaskJuggler: Error in scenario plan: No need to specify dependency X multiple times for task Y.

Closes #32

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (4a83831) 95.01% compared to head (6b642b6) 95.17%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #33      +/-   ##
==========================================
+ Coverage   95.01%   95.17%   +0.15%     
==========================================
  Files           1        1              
  Lines         281      290       +9     
==========================================
+ Hits          267      276       +9     
  Misses         14       14              

Flag	Coverage Δ
unittests	95.17% <100.00%> (+0.15%)	⬆️

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[Ben2022]

Thanks a lot. It looks good. Let's test it in real like with Bert.

[0xBDEF]

@JasperCraeghs : I reviewed and tested it. It is OK according to me. I can not approve, so will you ask @Ben2022 to approve or do you make me the approver?

[Ben2022]

Approved by Bert