Re-doing security for GS2

[ak19]

Preventing XSS the correct way.

Based on ​https://www.owasp.org/index.php/XSS_%28Cross_Site_Scripting%29_Prevention_Cheat_Sheet

securitytools.cpp based on OWASP's Java ESAPI: ​http://code.google.com/p/owasp-esapi-java/source/browse/trunk/src/main/java/org/owasp/esapi/codecs/

Changesets:

http://trac.greenstone.org/changeset/28888

http://trac.greenstone.org/changeset/28898

http://trac.greenstone.org/changeset/28899

http://trac.greenstone.org/changeset/28909

http://trac.greenstone.org/changeset/28911

http://trac.greenstone.org/changeset/28912

http://trac.greenstone.org/changeset/28913

http://trac.greenstone.org/changeset/28930

http://trac.greenstone.org/changeset/28948

http://trac.greenstone.org/changeset/28996

Initially we tried to use the OWASP C++ package. We no longer use it because when we tried it, a lot wasn't implemented yet, so we wrote our own c++ code for just the functions we needed in the new securitytools.cpp file.

Changesets to runtime-src back when we were trying to compile the owasp-for-c++ package:

http://trac.greenstone.org/changeset/28886

http://trac.greenstone.org/changeset/28910