Merge pull request #17 from goehle/master

XSS Fix
Merge pull request #20 from openwebwork/release/2.6

Periodic update from release/2.6 to develop
Protect HTML::Scrubber from undefined arguments
remove stray semi-colon
Merge pull request #21 from mgage/release/2.6

Protect HTML::Scrubber from undefined arguments
Remove a redundant definition of _PGbasicmacros_init{}  subroutine from the PGbasicmacros.pl file
Merge branch 'release/2.6' of https://github.com/openwebwork/pg into release/2.6
Merge pull request #22 from mgage/release/2.6

Remove redundant _PGbasicmacros_int {}  subroutine from PGbasicmacros.pl
Added comments to the probability routines.
Added a new routine to generate a list of normally dist. random numbers.
Added routines associated with exponentially distributed random numbers.
Fix off-by-one effect of number of attempts.

This makes the showHints work properly.

.
Added a routine to calculate the five point summary.
Cleaned up the comments and added info about the optional parameter.
Provide better solution to the numOfAttempts issue

Insures that the number of attempts defined in the environment is correct.
It is the sum of the number of incorrect attempts, the number of correct attempts
and the number of ungraded attempts (which is 1 or 0 depending upon whether an
answer has been submitted).
The calculation is done in PG.pm
Merge pull request #23 from mgage/release/2.6

Fix off by one bug in number of attempts
Fix correct_ans for Compute() when the result is a constant, and move creation of correct_ans_latex_string to Compute() so it properly corresponds to the correct answer string.  For answers not created through Compute, move creation of correct_ans_latex string to cmp() rather than cmp_parse(), since the latter may not be called (e.g., for blank answers), leaving no latex string.
Merge pull request #24 from dpvc/release/2.6

Fix correct_ans for Compute() when the result is a constant
Fixes problem with pi (and i,j,k) not being retained as a named constant, but being replaced by their values.  This was introduced accidentally by commit 261ba03f0e87c867efdbf32b8e2692e1485cdd1.
Merge pull request #25 from dpvc/fix-pi

Fixes problem with pi (and i,j,k) not being retained as a named constant