Notification of string changes

Author: Tim Hunt
MDL-20636 numerical qtype: assorted changes
1. database upgrade to merge instructions into the questiontext field,
and remove the UNITDISPLAY option.

2. Changes to the validation in deferred feedback mode, so students
are warned about incomplete answers.

3. Using this to wark students if they enter an answer that is not
recognised as a number.


http://git.moodle.org/gw?p=moodle.git;a=commit;h=5d2465c3f4b5e0644d5daa830fdf478c61642f4b
http://github.com/moodle/moodle/commit/5d2465c3f4b5e0644d5daa830fdf478c61642f4b

+ 2.1 en [editableunittext,qtype_numerical]
+ 2.1 en [unitposition,qtype_numerical]
- 2.1 en [numericalinstructions_help,qtype_numerical]