image filenames with multiple dots

[germano2239]

When working with images containing multiple dots in the filename, ie "1590845793.5.png" the generated mask files contain only the part before the first dot, ie "1589461554_mask.png"

expected behaviour: preserve the whole filename, ie "1589461554.5_mask.png"

solution: replace all the instances of file.baseName() to file.completeBaseName() in image_canvas.cpp