Pysigma

Bugfix (unnecessary *attr* import)

* Additional common log source definitions (moved from Splunk backend)

* **BREAKING CHANGE:** ConditionFieldValueInExpression was removed. This can break existing backends.
* Moved handling of in-expressions completely into the backend.

* Extended processing item tracking to rule level.
* Added processing conditions that allow to check if a processing item was applied.
* Added negation of processing conditions.

**Full Changelog**: https://github.com/SigmaHQ/pySigma/compare/v0.4.4...v0.4.5

What's Changed
* fix: do not accept invalid conditions by gaelmuller in https://github.com/SigmaHQ/pySigma/pull/39
* Fix: encoding issue in SigmaCollection.load_ruleset() method in collection.py by mbabinski in https://github.com/SigmaHQ/pySigma/pull/40


**Full Changelog**: https://github.com/SigmaHQ/pySigma/compare/v0.4.3...v0.4.4

Bugfixes

What's Changed
* Fixes: missing of them and unescaped regular expressions by gaelmuller in https://github.com/SigmaHQ/pySigma/pull/37

New Contributors
* gaelmuller made their first contribution in https://github.com/SigmaHQ/pySigma/pull/37

**Full Changelog**: https://github.com/SigmaHQ/pySigma/compare/v0.4.2...v0.4.3