PAINTROID-693 File not found when loading temporary copies

[JulianJautz]

Removed bug where path to temp file was set incorrectly and therefore image could not be loaded.

• streamlined saving and loading of temp file
• closed streams

https://jira.catrob.at/browse/PAINTROID-693

in addition, avoided kryo buffer underflow when app is started and no temp file available
should solve:
https://jira.catrob.at/browse/PAINTROID-655

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