Use in-memory keys for signing.

[NilsOliverLinden]

*This allows to provide password and key via project properties instead having to use gradle.properties

Signed-off-by: Nils-Oliver Linden

Overview

Provide password and key for signing via project properties instead of gradle.properties

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Definition of Done

• There are no TODOs left in the code
• Method preconditions are checked and documented in the method's Javadoc
• Change is covered by automated tests (unit and/or integration tests)
• Build has passed

[coveralls]

Coverage remained the same at 92.681% when pulling 892dffd on NilsOliverLinden:master into ad579b0 on TNG:master.