Displacement ASDs used for the Cosmic Explorer science traceability matrix

For a 40 km and 20 km long CE, four variants are given. The file naming convention is
* 1p5MW: 1.5 MW arm power
* 1p0MW: 1 MW arm power
* aLIGO_coat: aLIGO coatings
* Aplus_coat: the nominal A+ coatings with half the coating thermal noise as the aLIGO coatings

The nominal CE design has 1.5 MW arm power and uses the A+ coatings.

See CE_STM_strain.zip for strain ASDs.
