documenting. Removed some done todos, and added a few more, mostly to do
with finishing off the documentation.

debugging lines as the function has changed name.

hopefully to be a bit more readable. Only call session_start() in the
create_session method if the session is not started, I am noticing some
occasions where it appears that a session has started by $_SESSION is
empty.

  * Re-organised the file a bit, to better logically group some stuff
  * Renamed the log_dbg function to log_debug
  * Added a third parameter to the logging functions to say whether a
    backtrace is required.
  * Fixed up projectname in default exception handler.

submitted file value correctly for file fields. Moved the hsc function to
lib/mahara.php

element types.

* get_rows()
* get_rows_select()
* get_rows_sql()

people don't have to do silly isset() checks when using rules.

than *_$plugintype

login form.
Made a method that returns the element with the given name, which makes
some other methods shorter.
Don't pass hidden elements to the form element renderer, they're not
needed. Although some thought might need to go into how exactly they will
be placed later.