Only return token descriptions if $type is 'node' or 'all'... Also added token_user.inc, providing basic user account tokens.

Fixing some blindingly obvious errors in the static token caching. Should now work when called many times in a row.

Adding support for the full range of core node tokens. Creation and modification dates, first taxonomy term, etc. Should be roughly compatible with pathauto. Also added a themed help function for use in entry forms.

Initial commit of token.module, an API for placeholder substitution. Allows modules like custom_breadcrumbs, pathauto, etc to all leverage the same integration code.