moved filedesc to own define outside control

also created control_defs.rng and edited .gitignore
removed control, referenced through include
removed e.ead from defs;; create customization
renamed, removed, and rearranged files
added namespace to ead3.rng, fixes to defs

several attrs were not optional
added new ns for undeprecated schema
moved files; rewrote mk_dtd.sh; new ead3.*
removed xsd_documentation, xslt
Merge branch 'modular_design' into develop