Bump versions for rc2 release

Merge pull request flame-engine#515 from flame-engine/develop

0.28.0 release

Luan's line

Merge pull request flame-engine#475 from flame-engine/develop

0.27.0 release

Merge pull request flame-engine#455 from flame-engine/develop

0.26.0 RC

Merge pull request flame-engine#444 from flame-engine/develop

0.25.0 RC

Merge pull request flame-engine#411 from flame-engine/develop

0.24.0 RC

Merge pull request flame-engine#405 from flame-engine/develop

0.23.0 RC

Merge pull request flame-engine#385 from flame-engine/develop

0.22.1 RC

Merge branch 'develop'