Fix problem with zoomin storyview and hidden sidebar

Fixes #933
Boot prefix should preserve $tw in the browser

This change allows raw markup tiddlers to preload configuration values
into the `$tw` global
Add support for custom password prompts
Prompt twice when setting password

Fixes #364
i'm not sure what i'm doing...
Merge pull request #943 from fghhfg/patch-4

CLA signature from @fghhfg