Clean up rules

- [ ] We don't need BrowseObject rules to have properties that legacy doesn't expose. This will save memory usage as we won't be moving around those values. First task is to determine exactly which properties are exposed by legacy, so we can match. See comment for more info: https://github.com/dotnet/project-system/issues/2966#issuecomment-367222311
- [x] We should also check as part of this and make sure all of the rules are consistent across None/Content/Compile etc. These files should be identical apart from their Page.Name attribute, and the value of DataSource.ItemType. (~#4635~)
- [ ] Consistently apply DoNotCopyAcrossProjects
- [x] Clean up space, and layout of the elements attributes, so that it is identical across all rules - makes it easier to diff/read. (~#4620~)
- [ ] Add PersistenceStyle="Attribute" at the data source level for the rule
- [ ] Figure out default properties (such as datasource for a property, and see if you need to restate them - if not remove them).
- [ ] Consistently name all rules; RuleName.xaml, or RuleName.BrowseObject.xaml
- [x] Move rules into sub directories for different types to help find them, one for "Items", "Project", etc (~#4618~)
- [x] Finally we don't need localisable strings on non-Visible properties, since they're not shown to the user anyway (~#4270~)
- [ ] Ensure all visible browseobject properties have display names (and descriptions?)
- [ ] Write tests to ensure we don't regress any of the above (started with ~#4641~)
- [x] Test for xaml files included in CommonFiles.swr (~#4967~)
- [ ] Test for xaml files in design time targets (and neutral directory as appropriate?) (from #4775)
- [ ] We currently have CustomTool and Generator properties in some cases - do we need both?