Here are some notes on the new item refactoring:

I'm writing some general-purpose routines to support managing content
from multiple locations, in multiple formats.

== location ==
A tbwiki "item" is a logical unit of the wiki, and can be one of the
following:
 * page
 * block
 * section
 * row
 * field

A page is a whole file. A block is an item inside a file, defined by the
triple-brace syntax.  A section is an item inside a file, defined by the
header syntax.  A row is something that can be inside a page, block, or section.
This is used to express moin table rows.  A field can be a single-line entry
appearing on a page, and defined by the definition list syntax.

== content_format ==
Each item is expressed in the raw text in a format:
 * tbmarkup - this is page data, and may hold sub-items, but does not itself express a record
 * moin_table - this is a set of rows of moin-formatted table lines (starting with ||)
 * tbattr - this is a single record in my 'config' format (supporting single and multi-line entries, and comments
 * tbwikidb - this represents data attributes with definition entries and sections (in tbmarkup)
 * json - usually whole-page, supports single, multi-line and list entries
 * yaml - usually whole-page, supports single, multi-line and list entries, as well as comments and ordering
 * moin_table_row - this defines a single record in a moin_table

== item_class ==
A new set of routines is supposed to replace all previous access and update
routines for content, and allow different systems to access data items in
the wiki in a uniform manner.  The different systems that need to access
the items are:
 * processors
 * tables
 * data handler (for tbclient)
 * other external engines (Fuego)

The idea is that items are addressable with a uniform resource string.

== item_class routines ==
Here are the functions supported by the new item_class:
 * __init__(name, location, source_file, parent)
 * get_content() - load the content from it's source
 * evalute_content() - execute processor, if any, for the content
 * to_html() - convert item to html (for output)
 * content_to_data() - convert content into data (parse it)
 * data_to_content() - convert data into content (format it)
 * update() - update one element of the data with a new value
 * set_content() - push this content to parent (container item)
 * write_content() - put content back on disk

internal helper routines:
 * data_to_html() - convert data representation to html

== example uses ==
 * in main page wiki:
    * show:
       * page = item_class(req.page_name, "page", req.page_filename)
       * html = page.to_html()
    * in section edit_form:
       * page = item_class(req.page_name, "page", req.page_filename)
       * section = item_class(section_name, "section", req.page_filename, page)
       * put section.content into edit form
    * in section_edit action:
       * page = item_class(req.page_name, "page", req.page_filename)
       * section = item_class(section_name, "section", req.page_filename, page)
       * section.update(value_from_form)
       * section.set_content()
       * page.write_content()
    * in Processor:
       * parse_conf(block)
    * in data_handler:
       * get_page_item
       * put_page_item
    * in table:
       * for source in source_list:
          * get_record(source)
            * page = item_class(req.page_name, "page", req.page_filename)
            * record = make_record(page)
               * data = page.content_to_data()
               * add field stuff
          * format for table