add documentation not to use the key-field separator

[davidby-influx]

A tag formatted similar to

rule=RUN_TEST#!~#runRuleSteps

caused bad behavior from the character sequence #!~#

, but don't see any mention of those characters in the docs here:

https://docs.influxdata.com/enterprise_influxdb/v1/write_protocols/line_protocol_reference/#special-characters

However, in local dev environment I tried to replicate and found that while it does actually query correctly, the export is generated incorrectly.

[jstirnaman]

@davidby-influx What do you mean by "key-field separator"? Is that for line protocol or CSV?

[davidby-influx]

@jstirnaman - it's the internal separator used in TSM files to separate tag values from fields. So, never seen by end-users, but used all over to parse the TSM series meta-data.