[raster] raster2pgsql ability to override the filename column

[robe]

I was actually surprise to find out we don't have this feature.

We have a -F to include a filename column and -f to override the default raster column name, but I couldn't find how to override the filename column.

Main usecase is for appending to an existing table where the filename field may not be called filename.

[dustymugs]

Added in r11200.

[robe]

Wow you are so productive in the air we should keep you up high