These changes implement some better controls for controlling uploads.

1) There is a new site-wide configuration variable called maxbytes,
   which provides an upper filesize limit for all (student) uploads.

2) There is a new course-level variable called maxbytes, which further
   limits uploads within a course.

3) There is a new maxbytes field for forums, which further restricts
   the size allowed in a particular forum.  There is also a new config
   variable in the module configuration to specify a default size
   to use when defining a new forum.

4) Assignments already had a limit, but this is now aware of the other
   limits, and like forums there is now a settable default value.

5) Finally, the sizes of files (Gb, Mb, Kb, bytes) is now translatable
   in the language packs.

lib/db/postgres7.sql

@@ -26,6 +26,7 @@ CREATE TABLE prefix_course (
    numsections integer NOT NULL default '1',
    showrecent integer NOT NULL default '1',
    marker integer NOT NULL default '0',
+   maxbytes integer NOT NULL default '0',
    visible integer NOT NULL default '1',
    timecreated integer NOT NULL default '0',
    timemodified integer NOT NULL default '0'