Sanitize csv export data

Sanitize csv export data by stripping leading '=' or '@' characters from
strings and type casting numbers. Format as proper csv output using
PHP's fputcsv() function which will quote and escape output as
necessary.

Bug: 58307
Change-Id: Ia19ad10bc172adce5f6e16177404d3ef4dc8c4fe
Merge "Sanitize csv export data"