Baseline is JDK 11 and jetty 11

[azagniotov]

This PR belongs to ticket #451

[codecov-commenter]

Codecov Report

Merging #452 (a2fa729) into master (448eb2d) will increase coverage by 0.18%.
The diff coverage is 91.30%.

@@             Coverage Diff              @@
##             master     #452      +/-   ##
============================================
+ Coverage     97.03%   97.22%   +0.18%     
- Complexity      819      821       +2     
============================================
  Files            64       65       +1     
  Lines          2668     2664       -4     
  Branches        277      276       -1     
============================================
+ Hits           2589     2590       +1     
+ Misses           47       43       -4     
+ Partials         32       31       -1     

Impacted Files	Coverage Δ
...ov/stubby4j/handlers/AbstractHandlerExtension.java	100.00% <ø> (ø)
...agniotov/stubby4j/handlers/AdminPortalHandler.java	73.33% <ø> (ø)
.../stubby4j/handlers/AjaxResourceContentHandler.java	100.00% <ø> (ø)
...agniotov/stubby4j/handlers/StubsPortalHandler.java	100.00% <ø> (ø)
.../strategy/admin/AdminResponseHandlingStrategy.java	86.36% <ø> (ø)
...gy/admin/AdminResponseHandlingStrategyFactory.java	100.00% <ø> (ø)
...andlers/strategy/admin/DeleteHandlingStrategy.java	97.72% <ø> (ø)
...j/handlers/strategy/admin/GetHandlingStrategy.java	97.29% <ø> (ø)
.../handlers/strategy/admin/NullHandlingStrategy.java	100.00% <ø> (ø)
.../handlers/strategy/admin/PostHandlingStrategy.java	100.00% <ø> (ø)
... and 11 more