walkthrough: use correct css class for intro message of the "lines" chapter
walkthrough: increase timeout for revealing road subgrid
200ms seems to be too low, because the fade-in transition seems to take 250ms and an the unfinished animation can cause troubles.
this fixes #1742
add missing context parameter to call of intro.pad() in method retry() for incomplete way drawings
Merge pull request #1744 from tyrasd/patch-walkthrough-lines-tooltip

Fixes some walkthrough glitches