Basic videotools plugin.

* Adds support for MPEG and Matroska video files (renaming and fingerprinting only, no tagging)
* $is_video() and $is_audio() scripting functions (based on file extension).
Added support for the hachoir module for basic metadata parsing.

Now supports MPEG, QuickTime, Matroska and AVI files.
Added mov and avi to video format extensions.
Fixed file header.
Workaround for Picard ignoring extension objects not part of the main module.
Use enzyme instead of hachoir as a more lightweight dependency.

Directly include enzyme. This should allow the usage of this plugin under Windows.
Handle enzyme parsing errors.
Add WebM support.
Use presence of actual video track instead of file extension for is_video().

For the formats natively supported by Picard we still use the extension list.
Increased API version because this plugin uses zero arg script functions (and I have no intention to change this).
Merge pull request #3 from phw/videotools

Videotools