Factor/To do/Docs

• rethink handbook organization
• clarify stack-checker and compiler errors docs; add a summary with a bullet-point list of 'why doesn't my code infer?'

Done:

• help lint: flag words which are not classes but have a $class-description
• document decode-input, encode-output
• more prominent mention of image saving
• document how factor UI modifiers map to native modifiers
• document gesture handling differences
• document graft/ungraft idiom for GL resources
• document words.
• with-ui is undocumented
• document that macro expansions cannot involve lambdas
• This should be a help article: http://factor-language.blogspot.com/2008/05/ssltls-support-added.html
• document locals in literals feature
• document see-methods
• document io.encodings.string
• . and pprint: add a warning about large objects
• mention help word, and C+S+h more prominently in cookbook