Whitespace/tabs cleanup
Whitespaces/tabs cleanup
Wrap document reader into try/catch block
Get rig of unused old code
Added 'found in page cache' URL processing.

If URL has been found in local storage, its timestamp is being checked,
and we only process URLs which were uploaded before current engine was started.

Otherwise means system already downloaded URL from the internet after current
downloading session (current engine) was started.

Also added if-modified-since header when trying to download URL which already
exists in the local storage.