changed http to https connection
Merge pull request #1020 from Catrobat/ServerCallTestFix

Fix for failing ServerCallTests
fixed issues #910, #909 and #906

Feature_Backpack_Enabled can be set in build.gradle

changed the strings accordingly

removed checkstyle warning

added check if BuildConfig.FEATURE_BACKPACK_ENABLED is true
asf
Merge branch 'issues910_909_906' of https://github.com/Catrobat/Catroid into issues910_909_906