- manual zooming now based on logarithmic scale
- new _user_zoom limits
- _base_zoom completely separated (and removed) from _user_zoom
- _scale_up completely separated from _fit_mode
- As a result, no upscaling is performed when using "Manual zoom mode".


git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@900 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Check if file still exists before trying to add it to library DB.

MComix incorrectly assumed that all files in the "Recent" database
would still exist at the time the database migration takes place.

Fixes #4

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@901 ef8490bc-f317-4725-81ed-e95a9aca1bcf