Add bounds and center to metadata in MBTiles file

[ssokol]

Not a huge deal, but having the bounds and center coordinates in the metadata would make it slightly faster for my use case. My tile server indexes the MBTiles files in a given directory then uses the bounds and/or center values to find the required file when it receives a request.

Here's what tilemaker sets as metadata for those values:

bounds|-106.645646,25.837377,-93.508292,36.500704
center|-100.076969,31.169041,7

[N129BZ]

If processing single area chart(s), the app will now add bounds and center values to the metadata table in each mbtiles database.
These new metadata fields will be not be present if processing any of the full charts, since those are actually comprised of multiple individual geotiffs which each have individual extent data, making any overall calculation of extents more involved than I have time or inclination to deal with.

[N129BZ]

P.S., also added a new settings.json key+value: centerzoomlevel which defaults to 7. Example below.

In settings.json:

    "tileimagequality" : 40,
    "blendpixels" : 30,
    "zoomrange" : "0-11",
    "centerzoomlevel": "7",   <= new setting
    "dbextension": "mbtiles",
    "externaldbfolder": "",
    "addoverviews": true,

[ssokol]

Apologies - I was out for part of the weekend. I was specifically referring to the bounds for individual VFR sectionals. What you've added is exactly what I needed. Thank you very much!