V14: Rename new projects (#15836)

* Rename Web.UI.New back to Web.UI

* Delete new backoffiec folder

* Rename client project

* Add new submodule

* Update template csproj

* Remove more mentions of new

* Add missing views

* Moving up the "Umbraco.Web.UI" proj reference, so that it is the first project listed in solution file (.sln) since it will be selected as startup one in VS by default.

* don't include grid

* Update with section of how to get started with backoffice

* Update .github/BUILD.md

Co-authored-by: Elitsa Marinovska <21998037+elit0451@users.noreply.github.com>

* Add line about white page

---------

Co-authored-by: Elitsa <elm@umbraco.dk>
Co-authored-by: Elitsa Marinovska <21998037+elit0451@users.noreply.github.com>

src/Umbraco.Cms.Targets/Umbraco.Cms.Targets.csproj

@@ -62,7 +62,7 @@
   <!-- Generate JSON package schema on build (and before copying to project) -->
   <Target Name="GenerateUmbracoPackageSchema" BeforeTargets="Build;CopyUmbracoJsonSchemaFiles" Condition="!Exists('$(_UmbracoCmsPackageSchemaReference)')">
     <Message Text="Generating $(_UmbracoCmsPackageSchemaReference) because it doesn't exist" Importance="high" />
-    <Exec WorkingDirectory="$(MsBuildThisFileDirectory)..\Umbraco.Web.UI.New.Client" Command="npm run generate:jsonschema -- --out &quot;$(MSBuildThisFileDirectory)$(_UmbracoCmsPackageSchemaReference)&quot; tsconfig.json UmbracoPackage" />
+    <Exec WorkingDirectory="$(MsBuildThisFileDirectory)..\Umbraco.Web.UI.Client" Command="npm run generate:jsonschema -- --out &quot;$(MSBuildThisFileDirectory)$(_UmbracoCmsPackageSchemaReference)&quot; tsconfig.json UmbracoPackage" />
   </Target>
 
   <!-- Remove generated JSON package schema on clean -->