Use sjlf4j-api instead of impl in SDK

[kkocel]

Use log4j-slf4j-impl in samples in tests. Logging instructtions in the Readme.md

Fixes #271

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• [x] My code follows the code style of this project
• [x] My change requires a change to the documentation
• [x] I have updated the documentation accordingly
• [x] I have read the README document
• [ ] I have added tests to cover my changes
• [x] All new and existing tests passed

License

• [x] By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[kkocel]

@Shreyas-vgr so it's good to merge?

[SCKelemen]

Maybe this should be prioritized: https://www.lunasec.io/docs/blog/log4j-zero-day/

[kkocel]

@SCKelemen yes, I bumped dependencies to fix this 0 day, @Shreyas-vgr another reason for the merge :)

Fortunately, my PR removes log4j impl from the production code so log4j won't be added into the user codebase.

[htmldoug]

@ShenChen93, sorry for the direct tag, but given the severity, can you please help get this merged and released?

[Shreyas-vgr]

Merged the change to mainline, thanks @kkocel for the PR