Made xwebmail work with new handlers package.
Pulls important headers from the database and provides extremely basic folder
view on webpage.
Reverted layout customizations returning folder view to original wider width.
JS App now handles all the rendering, index.html only contains placeholder
with background to indicate loading.
Add ability to dump headers or mimetypes for original messages.
Add ability to dump all messages, instead of just hashes listed.
Add new command cmd/headers to import all headers from messages in table
original. Utility can work incrementally or do fully table imports.
Moved 'fetch all original messages' code to db/util.go. Added conditional
version given table name that will only return original messages that do not
have matching hashes in the specified table.
