Instances of escapeshellcmd() where escapeshellarg() is required

Specifically here and here and possibly here (cancel that third one, it's already made sanitized)

In each of these cases, a path to a file is being passed into the invocation of exec() without being escaped; escapeshellcmd() is being relied upon instead, which cannot account for cases where the path needs to be escaped and in quotes (e.g., if there is a space in the path).

While this is typically not an issue (Large Image typically runs these on a sanitized temporary file), modules implementing these commands and others that rely on them, such as islandora_large_image_imagemagick_convert, will throw warnings and fail to function when providing files with spaces in them.

These lines should be modified so that any variables referencing paths are escaped through escapeshellarg().