UI and validation for the new signup system, actual backend functionality is started but mostly missing

Makes password check function in session class public

Allow members to specify a blog feed in the options component, and generate planet configuration files dynamically. Fixes #64

However, bodged it into the pagemap as an emergency fix and opened ticket #61

from the better-late-than-never department, here's a stupidly overcomplex yet incomplete way of adding new books. Doesn't deal with tagging yet, but better than nothing, don't you think? Maybe someone else should rewrite the whole library component in an afternoon following KISS principles soon ;-)