Remove checking for missing wiki folders

Thus undoing 744245ea3249446fd15f504190efb1d828935d01 because of #1002
Coloured warnings and errors under Node.js
Add warning when serving a non-existent wiki folder

The warning will be yellow to make it noticeable
Report command errors through $tw.utils.error

So that we get the new colourisation
Use titles when dragging links to non-TiddlyWiki destinations

Handily, this means that you can drag tiddler links from the sidebar
into the text editor, making it easier to create links and
transclusions.
Move search result count logic out of translations

Also fixes a problem pointed out by @Evolena whereby the advanced
search counts hadn’t been adjusted to remove `$:/temp/advancedsearch`
from the search.