To generate XLF files with ng-xi18n we could use the format parameter "xlf" or "xlif". The real name is "xliff" not "xlif", so this probably was a typo. This PR adds "xliff" as can be expected
Inlcuded fixes:
- include preamble in generated source map
- always add a mapping for line/col 0 so that the
generated sourcemap is not sparse
- use a uniue sourceUrl for inline templates even
in the AOT case