docs: document feature analysis for slide size

* remove now-dead scripts directory and contents
docs: document Enumerations feature analysis
enum: rename Enumeration to Enumeration_OLD
enum: add Enumeration classes and tests
enum: refactor MSO_AUTO_SIZE to new Enumeration
enum: reimplement MSO_COLOR_TYPE in pptx.enum.dml

Import moves from pptx.enum to pptx.enum.dml
enum: reimplement MSO_FILL_TYPE in pptx.enum.dml
enum: reimplement MSO_THEME_COLOR in pptx.enum.dml
enum: reimplement MSO_VERTICAL_ANCHOR in enum.text
enum: remove now-dead Enumeration_OLD
enum: reimplement PP_ALIGN in enum.text
enum: delete dead pptx.spec.pml_parttypes
enum: remove dead spec.ParagraphAlignment

* use to_xml() and from_xml() instead of TAT
enum: remove dead TEXT_ANCHORING_TYPE
enum: reimplement MSO_SHAPE_TYPE in enum.shapes
enum: add PpPlaceholderType and ST_PlaceholderType
enum: add ST_Direction and ST_PlaceholderSize
enum: refactor and move MSO_AUTO_SHAPE_TYPE
reorg: combine pptx.spec.default_content_types

also:

* change Image.ext to not include leading period
enum: take prst from MSO_AUTO_SHAPE_TYPE

remove redundant definition in pptx.spec.autoshape_types dictionary