Adds newsletter to installer

With the good ol' V6 installer code, ahhh the smell of code patina
Fixes failing dropdown prop editor tests
U4-4575 - property converters use wrong source value
U4-4559 - tests
Adds AddRelation and missing events in RelationService from v7 into v6
Ports behaviour from membershiphelper from v7 to 6 to make them the same
Fixes: U4-4581 Hotkey - Click on disabled element
Fixes: Password is not saved when using the Register snippet
Merge branch '6.2.0' of https://github.com/umbraco/Umbraco-CMS into 7.1.0

Conflicts:
	src/Umbraco.Core/Services/IRelationService.cs
	src/Umbraco.Web/Controllers/UmbRegisterController.cs
Merge branch '7.1.0' of https://github.com/umbraco/Umbraco-CMS into 7.1.0
Fixes: U4-4558 U7 Macro Parameter Editors needs some love!

Adds some config to the media picker and fixes thumbnail issues
Merge branch '7.1.0' of https://github.com/umbraco/Umbraco-CMS into 7.1.0
Fixes failing macrospec tests

doooh, it referenced marcoParamsDictionary - instead of
macroParamsDictionary - whats up with that Marco guy?
Resizing safeguards to ensure we only return positive
Partially fixes: U4-4479 Cropper preview in backoffice is a bit off from the actual crop

Makes the cropper card UI reset on save, ensuring changes populate
Fixes: U4-4332 MediaPicker - Typealias is hardcode several places
Missing files in last commit
Sets zoom throttle to 100 instead of 300

To limit the number of re-calculations, but still keep it somewhat
fluent
Fixes U4-4278 Multiple RadioButtonList on one Document

Manually applying pull request as it's a bit faster to copy&paste instead of resolve merge conflicts
Update version of ImageProcessor and refer to NuGet in the csproj instead of the bin (!)