feat: use custom land cover maps

[12rambau]

• add a panel to reclassiffy Image into UNCCD classes
• display the land cover map on the map
• creaate advance parameters to hide custom matrix and landcover
• create custom assetSelect that only accept Images reclassified into the UNCCD land cover mapping
• use it in computation and naming
• add safety to ensure user set everything before computing the indicator Fix #53