v2.2.0

This release has a huge modification regarding the Filters feature.
It now has a list of all Sieve scripts and you can activate/add/edit/delete any script.
This is achieved also based on

• request: RainLoop#2051
• bug: #49

Further:

• reduced webpack related code
• slimmed down languages
• improved Knockout observable and observableArray
• slimmed down code due to Knockout changes
• CSS improvements
• merged RainLoop v1.15
• other tiny changes and renamings