when cleaning build files, don't clear component by default
Added 15-minute slot selection to 1.5.1
tweaks to ms-doodle-com's pull request for finer event selection granularity:
- identifiers in code renamed to "granularity", because not specific to selection (also event redragging)
- granularityMinutes automatically defaults to the slotMinutes option
- very minor code rearchitecting
move granularity demo into ./tests/granularity.html
implement granularity for events dragged from all-day-slot into time-slot