geshifilter 5.x-2.0

First release of overhauled GeSHi filter module:

main differences with previous version (5.x-1.x branch):

• Language tags, e.g. you can enable tags like "<java>".
• Configurable generic tags.
• option to choose between tags styles "<code>", "[code]" or both
• guided filter conflict solving: conflicts with other filters like the HTML filter are detected and suggestions are given how to solve them.
• better/easier UI (languages got their own settings page, better handling of error conditions, ...)
• options for CSS mode: inline or with stylesheet.
• Elaborate filter tips and documentation
• added callback to clear the filter cache (handy after changing the settings)
• Many bug fixes and tweaks