Author: Rajesh Taneja
MDL-35047 tool_xmldb: Added missing strings for xmldb
http://git.moodle.org/gw?p=moodle.git;a=commit;h=b5f0654fd21df732b1273994f84509e80e674e40
http://github.com/moodle/moodle/commit/b5f0654fd21df732b1273994f84509e80e674e40
+ 2.2 en [duplicateindexname,tool_xmldb]
+ 2.2 en [indexnameempty,tool_xmldb]
+ 2.2 en [incorrectindexname,tool_xmldb]