add DataTables viewer for tabular data
replace DataTables pagination with virtualized/"infinite" scrolling
drop cached frames; make viewers survive session suspend/resume
make DataTables respond to changes in window height from the IDE
implement server-side data sorting by column (ascending/descending)
Merge remote-tracking branch 'origin/master' into feature/data-grid
use grid_data endpoint for both shape and data; show observations
handle promises and data in package environments
add DataTables and jQuery to installer and NOTICE; tweak table cell alignment
save a cached copy of viewer objects for use when source object is gone
persist data frames for viewing in the user scratch folder
improve data.frame coercion and treatment for non-data.frames
handle nulls and unexpected SEXP types gracefully in rownames
handle missing objects with less alarm; avoid DataTables error popups
send column metadata (data type, value ranges, etc) to client
create filter UI directly beneath column headers
working example of filtering by factors
add UI hooks to hosting view to toggle filter UI inside frame
move filter UI into popup (WIP)
apply the filter specified in popup