subtitle data model - adding accessors for internal fields
subtitle class - adding initial json storage

simply records line-number and content
subtitle class - adding field for summary

allows for quick overview of subtitles on the overview page
DEBUG: adding json dump to subtitle view page
subtitle class: adding subtitle revision history

tracks any non-equal line as a revision
compares stored line at line-number to input line of same line-number

currently requires all edits to not add or subtract lines
subtitle class: fixing updateSummary

was disabled while deciding on json structure
also: removing dependency on passed-in list, can be called externally now