revtex4-1.layout: remove hard-coded document class option

we must not use this option because the user must select the right one for every document and the other styles like aip etc cannot be used when aps is used.
revtex4-1.lyx: update template to fulfill the official rules

changes:
- the document must have the size US letter
- use the document class options and the content of the official REVTeX sample file
- amsmath and amssymb must always be loaded
status.21x: document recent change and correct a bug number