[PATCH 0 of 3 V6] hgweb: teach archive how to handle file patterns

[Angel Ezquerra]

Compared to the previous version this version adds an extra patch which modifies the templates so that this new feature is exposed through the web interface. It also (tries to) address Mads' comments.

Also note that the title of this series does not really fit the actual contents of the series anymore because this only teaches hgweb to download directories, not patterns. I kept the title to make it easier for patchwork to detect this new version of the series.