Merge branch 'development' - Version 1.6.0

Merge branch 'development' - Version 1.5.6

Merge branch 'development' - Version 1.5.5

Merge branch 'development' - Version 1.5.4

Merge branch 'development' - Version 1.5.3

Merge branch 'development' - Version 1.5.2

Merge branch 'development': version 1.2

Merge branch 'development' for version 1.1

Merge branch 'development': Version 1.0.1 - release on wp.org's repo

Merge branch 'hotfix_281'