add logger class
add some doc to logger
validate some media file properties; etag support
fire action when media file content changes
adjust logging text for 304 event
add cache to chapter printing
devalidate caches when media file has changed
move chapters logic into separate class
implement psc pages
fix module activation hook
resolve double-validation glitch
stop validation when encountering unexpected http code
show next scheduled validation time in backend
more descriptive validation module description
add asset validation module to defaults
switch psc in feeds to inline
logging module: log to db
use model toolkit for database logging
display log in dashboard
link to episode edit page