- use same generator as most other projects in aspnet repos
- were not using named arguments to resource methods anyhow
- update resources to use regular (numbered) format parameters
- adjust to new `Resources` namespace; no need for separate `using`
- use `Format...(...)` methods as necessary
- also cleared out most uses of `GetDocument` and `GenerationTasks` in MSBuild and strings
- temporarily fixed up T4 templates, adding Resources.tt (will remove custom generation soon)