Merchant sdk refactor credentials

[motokotomax]

Proposition to refactor: move credentials from plist to code.

• less files and code
• file with credentials will be ignore by git
• developer will be notified with crash, if he don't fill own creds
• need to update documentation, remove image with creds format

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[ValentinaIancu-Gini]

ohh wow super nice! I will bookmark this pr and try to apply as soon as possible in BankSDK and CaptureSDK.

Thank you!

[motokotomax]

Thanks for review, but initialization method changed, and this refactoring not needed any more