#587 COMPOSITE_TILE_DIR_STORE_MAX_AGE_MS and per layer refreshIntervals

[tariqksoliman]

Closes #587

Adds:

• ENV: COMPOSITE_TILE_DIR_STORE_MAX_AGE_MS=
  • "When using composited time tiles, MMGIS queries the tileset's folder for existing time folders. It caches the results of the these folder listings every COMPOSITE_TILE_DIR_STORE_MAX_AGE_MS milliseconds. Defaults to requerying every 30 minutes. If 0, no caching. If null or NaN, uses default. | number | default 1800000"
• refreshIntervalEnabled configuration option for Raster and Vector Layers
  • "If 'Time Enabled' and 'Refresh Interval Enabled', this layer will automatically refresh/requery its data every 'Refresh Every N Seconds'. This is useful when the layer's data updates at some uniform cadence. Be aware that this may be an expensive operation depending on the amount of data a layer needs and the number of layers that have this enabled."
• refreshIntervalAmount configuration option for Raster and Vector Layers
  • "If 'Time Enabled' and 'Refresh Interval Enabled', this layer will automatically refresh/requery its data every n seconds."