Fix bulk import parsing bug and limit concurrent client connections

[benjamingeer]

This fixes the parsing of properties in knora-base that are directly used in project-specific resource classes in XML bulk import data (e.g. knoraXmlImport__seqnum).

It also changes HttpTriplestoreConnector and SipiResponder so they block until getting an HTTP response, to ensure that the number of concurrent HTTP client connections won't exceed the number of instances of these actors.

Fixes #971.
Fixes #972.

[codecov]

Codecov Report

Merging #973 into develop will decrease coverage by 0.04%.
The diff coverage is 63.93%.

@@             Coverage Diff             @@
##           develop     #973      +/-   ##
===========================================
- Coverage    82.53%   82.49%   -0.05%     
===========================================
  Files          150      150              
  Lines        17004    17043      +39     
  Branches      1627     1623       -4     
===========================================
+ Hits         14035    14060      +25     
- Misses        2969     2983      +14

Flag	Coverage Δ
#integration	46.14% <57.37%> (-0.01%)	⬇️
#unit_e2e	81.32% <45.9%> (-0.09%)	⬇️

Impacted Files	Coverage Δ
...c/main/scala/org/knora/webapi/util/ActorUtil.scala	78.57% <ø> (+11.9%)	⬆️
...api/src/main/scala/org/knora/webapi/Settings.scala	90.09% <100%> (+0.3%)	⬆️
...g/knora/webapi/responders/v1/SipiResponderV1.scala	79.54% <56.52%> (-10.31%)	⬇️
...re/triplestore/http/HttpTriplestoreConnector.scala	83.41% <63.33%> (-0.48%)	⬇️
.../scala/org/knora/webapi/util/StringFormatter.scala	90.26% <80%> (+0.07%)	⬆️
...i/src/main/scala/org/knora/webapi/Exceptions.scala	34.78% <0%> (-4.35%)	⬇️
...org/knora/webapi/routing/v1/ResourcesRouteV1.scala	81.71% <0%> (+0.38%)	⬆️

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[subotic]

LGTM