OpenEMS/openems: 2021.6.0

Bug Fixes and Other Changes Update Angular to version 11 1698c8e375f07e72584cae6696715b073adb0d44 following https://update.angular.io/?l=2&v=10.0-11.0 Update to latest Ionic template e0753f493e95b0896ab1128faf789c1f13cf4656 using ionic start command and applying all files to OpenEMS UI RRD4j: fix default step seconds; improve post-processing 831c04d3dc73ce98ed70843678e42e4ad2e72197 default step seconds had been accidentially left at 1 second; should be 5 update datafile migration improve data post-processing for uneven split Continuous Integration: update node version to 15; npm version to 7 5592e96e2fd6da372ed9f0328847496805439a6a Fix UI build (#1419) Make variables public that are used in templates Clear warnings for "CommonJS or AMD dependencies can cause optimization bailouts" Set strictInjectionParameters and strictTemplates to false Docs: Fix Component Communication page ab69747f40b126df7999af1da8009e49e8e02ded https://openems.github.io/openems.io/openems/latest/component-communication/index.html Bump fastexcel from 0.12.3 to 0.12.7 in /cnf (#1418) Fix Fenecon Home Battery Capacity Calculation (#1421