Support marking and downloading multiple packages
Do not colorize empty values (aurel-empty-string)
Add support for refreshing (reverting) information

Also generalize functions for searching/showing packages.
Add link to maintainer's account to info buffer
Fix checking of outdated string
Add support for multiline parameters

Add more info about installed packages, including parsing multiline
values of parameters.
Some clean-up in docstrings
Add user options for mode names
Add option for ignoring empty values
Add `aurel-info-architecture' face
Improve docstring of `aurel-date-format'
Remove `aurel-filter-empty'

It is clearer to replace "empty" strings only during displaying
information.  Filtering on the early stage is not enough anyway as there
may not be some parameters (of installed packages) that should be
inserted in a list buffer.
Update README
Update version (0.4) and package commentary