Installer: Remove all configuration files on uninstall (fixes #378)

These configuration files may contain paths to the install directory, which
break when we are reinstalled into another directory.
Translations update

- Add Czech and Catalan translations
- Update French, Finnish, Hebrew, Indonesian and Slovak translations
- Add translation of new ServiceStartingFixed string in various languages

As usual, thanks to all translators!
WebMP hosting: Use different ASP.NET temp files directory

Use a directory in our own Cache directory as the Temporary ASP.NET files
directory, since we cannot write to the system one in Windows 8.