UI test improvements

[zawadz88]

This PR:

• increases test coverage by adding a bunch of UI tests for the sample app
• fixes UI test coverage by disabling Test Orchestrator which was not aggregating reports from all the tests
• fixes dependencies in the created pom.xml which disappeared after migrating to Gradle 4.1
• adds test butler to improve test stability
• adds a new artifact espresso-material-stepper to help with UI tests
• updates library version to 4.2.0

[codecov-io]

Codecov Report

Merging #199 into develop will increase coverage by 19.38%. The diff coverage is 100%.

@@              Coverage Diff              @@
##             develop    #199       +/-   ##
=============================================
+ Coverage      65.71%   85.1%   +19.38%     
- Complexity       202     260       +58     
=============================================
  Files             30      30               
  Lines            980     980               
  Branches          85      85               
=============================================
+ Hits             644     834      +190     
+ Misses           290     118      -172     
+ Partials          46      28       -18

Impacted Files	Coverage Δ	Complexity Δ
...main/java/com/stepstone/stepper/StepperLayout.java	77.01% <100%> (+35.71%)	82 <0> (+42)	:arrow_up:
...epstone/stepper/internal/widget/TabsContainer.java	94.73% <0%> (+3.5%)	18% <0%> (ø)	:arrow_down:
...epstone/stepper/internal/type/TabsStepperType.java	70.37% <0%> (+3.7%)	5% <0%> (+1%)	:arrow_up:
...one/stepper/internal/widget/DottedProgressBar.java	95.34% <0%> (+4.65%)	15% <0%> (+2%)	:arrow_up:
...e/stepper/adapter/AbstractFragmentStepAdapter.java	100% <0%> (+11.11%)	5% <0%> (+1%)	:arrow_up:
.../stepper/internal/widget/ColorableProgressBar.java	89.74% <0%> (+20.51%)	10% <0%> (+1%)	:arrow_up:
...com/stepstone/stepper/internal/widget/StepTab.java	93.16% <0%> (+26.08%)	28% <0%> (+2%)	:arrow_up:
...one/stepper/internal/type/AbstractStepperType.java	100% <0%> (+27.27%)	6% <0%> (+2%)	:arrow_up:
...stepper/internal/widget/RightNavigationButton.java	88.23% <0%> (+47.05%)	7% <0%> (+3%)	:arrow_up:
... and 2 more

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