Disable automatic type inference

[alfs]

Fields are automatically inferred to strings or numbers. This causes problems in some cases; in particular some long digitnumbers were turned into E-notation, for example 1231231231234 -> '1.231231E12'. This format was then refused by logstash since it didn't match the type.

In the json-format, it's possible to double-quote ""%key%"" to make it a string in the output; however the type conversion that happens before can still cause problems.

So there should be a way to disable this automatic conversion for specific fields, or alltogether.