Google Analytics: Custom Metrics and Dimensions supporting names + validation

[freiSMS]

Proposed changes

• Allow developers to define the index of google Analytics metrics and dimensions set by system (see here https://community.jovo.tech/t/google-analytics-custom-dimension-metrics-improvements/1510?u=andre)
  • fixes problem of overwriting developers custom definitions
  • readable code -> instead of setting "cd1" your are setting custom dimension 'UUID'
  • allow changing target custom definition without changing code logic
• Add "strict mode" via config -> will check if all needed system definitions are defined + are not mapped to same index
• make $googleAnalytics instance of class
  • -> gives access to features of used universal-analytics
  • -> enhance class with new method will no longer need second declaration on $googleAnalytics object and third definition on interface

Checklist

• My code follows the code style of this project
• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

[aswetlow]

Thank you so much, André