Add prefix to mbtiles, return 204 on no tile

[mtfurlan]

This adds a configuration option for a prefix to the mbtiles, so you can
store the tiles in other locations.

It also changes the no tile found 404 to a 204, as the mapbox team will
be doing:
mapbox/mapbox-gl-js#1800 (comment)

[daliborjanak]

Looks good. Thanks, but I would like to rename the variable mbtilesPrefix to something better. We are planning to add geopackage support in next days so it could be something like dataPath, dataSource or dataDir. What do you think?

[mtfurlan]

I would vote for dataSource, or maybe dataDir.

[klokan]

In our TileServer GL it is called root path - see JSON config at http://tileserver.readthedocs.io/en/latest/config.html

[daliborjanak]

I'm prefering data*. Root is often used as root of an app. But this variable as to be used also for folder structures - with serving without htaccess...

[klokan]

dataRoot or dataPath?

[mtfurlan]

dataRoot would work, it's still clear as to what it does.

[mtfurlan]

It's still mbtilesPrefix?

[daliborjanak]

2ead30d

[mtfurlan]

Fair enough.
Many thanks!