SOLR-111 : Validate JSONP callback function name to avoid XSS

[seboo]

callback function name in JSONP requests must match "[_\-A-Za-z0-9]+"

[jonenst]

Remove '-' and add '$' ? cf https://stackoverflow.com/questions/2008279/validate-a-javascript-function-name

(if you wanted to keep '-', you could put it at the end so that you don't have to escape it)

[seboo]

I modified the pattern to exclude "-" and include "$", and put it in properties file