[Clas12_verystrange] proposal update

[Lei Guo]

Hi, all,

I updated a few files, introduction, misscas, beam.tex (using  
Michael's simulation numbers), caspol.tex, spin-parity.tex, and so on.  
ALl minor changes. But they should be more readable now.
I also changed the refences.tex, they should be almost all be in order  
now, unless I missed a couple.

I also added Moskov's plot from g11 for identifying the neutron Xi0  
from K+K0 missing mass.

Lei
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