Make the size of the dialogue boxes changable

When you are saving an asset the name of the asset being saved is written on the top of the dialogue box in the format /<asset_name>/ , which usually is a long string but the size of the dialogue box is very small and this string is not readable. Also the user cannot change the size of the box as well which means cannot read the name of the asset being saved. This can be problematic as explained in #230 (closed) (closed bug).

The dialogue box for deleting an asset is also fixed in size. At the moment there is no name on the top of the dialogue box but it may become necessary in the future.