Update the CodeMirror SQL mode to contain a lineComment value (--) (#1813)
Update the CodeMirror SQL mode to contain a lineComment value (--) (#1813)

This PR adds a lineComment value to the %%sql cell mode. The effect of this is to allow for toggling comments with the Ctrl+/ keyboard shortcut via the CodeMirror comment.js addon.
parthea/datalab,googledatalab/datalab,parthea/datalab,googledatalab/datalab,googledatalab/datalab,parthea/datalab,parthea/datalab,parthea/datalab,googledatalab/datalab,parthea/datalab,googledatalab/datalab,googledatalab/datalab