Switching book info between metadata and filename

[minaev]

It should be possible to switch the bookshelf display mode between metadata view (metadata extracted from the file, if possible) and filename view (only filename, extension and size are displayed).

In filename mode the filename should be wrapped in two lines to use all possible space.

The reasoning behind the proposal is like that: many files in HTML and PDF formats contain some metadata, but the data are either incorrect or incomplete or irrelevant. In some cases it's better to turn the metadata off completely. Filenames may be even more informative. But such informative filenames are longer than usual and require more space.