refactor UI for plog-import

[anti]

Currently plog-import lists all images in upload directory and allows to select an album for each image or alternatively import all images to a single album.

Instead, I'm proposing that album selection should be removed for each picture, instead it should be possible to select individual images with checkboxes (or all images at once) and then select an album to import the selected images into.

Also, it should be possible to create a new album directly from that screen, just the way plog-upload works.