Added data for DPX expt 140425
Fixed abspath, join calls in 140429

Was specifying full package path os.path even though they had been
explicitly imported by name.
Commit of layout_140425 before refactoring

Refactoring to use shared implementations of analysis code in
dpx_assay.py
Doc/plots for DPX assay, 140425
Minor fixes to dpx_assay and plate_assay for plotting