Credit: original version done by Kirill Astashov of NetSpot (netspot.com.au),
finished and tweaked by sam.
This change adds conditional availability support for sections analagous to
that already available for activities. (Backend, UI, backup/restore.)
In order that this feature does not reduce performance, section cacheing has
also been added using a new course 'sectioncache' field analagous to modinfo.
The new feature integrates with activity availability so that activities
inside sections which are not available are automatically not available
themselves (meaning it works to restrict access).
From now on, all English strings use the new syntax. They are not
eval()'ed any more and the only valid placeholders are {$a} and
{$a->foobar}. No extra quotes escaping, dollar sign escaping and putting
double percent signs.
The modified files were exported from AMOS database repository in the
new syntax and were re-ordered by stringid. Standard GNU/GPL and PHPdoc
blocks are added. Where there was no copyright note so far, I added the
default one with Martin Dougiamas as the copyright holder.
Live long and prosper.