Blacklist pre-installed apps

[FHellmann]

Short description of what this resolves:

The user was not able to select pre-installed apps (like YouTube or Chrome).

Changes proposed in this pull request:

• The user can select every installed app

Does this close any currently open issues?

Fix #78

[codecov[bot]]

Codecov Report

Merging #90 into master will increase coverage by 4.28%. The diff coverage is 17.16%.

@@            Coverage Diff             @@
##           master      #90      +/-   ##
==========================================
+ Coverage   20.09%   24.38%   +4.28%     
==========================================
  Files          74       75       +1     
  Lines        1528     1534       +6     
  Branches       62       61       -1     
==========================================
+ Hits          307      374      +67     
+ Misses       1220     1158      -62     
- Partials        1        2       +1

Impacted Files	Coverage Δ
...g/uniatron/service/handler/PackageChangeModel.java	0% <0%> (ø)	:arrow_up:
...augsburg/uniatron/ui/setting/SettingViewModel.java	0% <0%> (ø)	:arrow_up:
...sburg/uniatron/service/handler/StepCountModel.java	0% <0%> (ø)	:arrow_up:
...urg/uniatron/ui/card/appusage/AppUsageAdapter.java	0% <0%> (ø)	:arrow_up:
...rg/uniatron/service/handler/StepCountDetector.java	0% <0%> (ø)	:arrow_up:
.../augsburg/uniatron/ui/setting/SettingFragment.java	0% <0%> (ø)	:arrow_up:
...rg/uniatron/ui/onboarding/OnBoardingViewModel.java	0% <0%> (ø)	:arrow_up:
...ni/augsburg/uniatron/service/StickyAppService.java	0% <0%> (ø)	:arrow_up:
...burg/uniatron/ui/shop/TimeCreditShopViewModel.java	0% <0%> (ø)	:arrow_up:
...urg/uniatron/ui/card/summary/SummaryViewModel.java	0% <0%> (ø)	:arrow_up:
... and 19 more