Added possibility to exclude labels and tag from the LTSV

[kayrus]

If you would like to store original JSON data in simple text format without additional labels and tags now you can use the following options for ltsv format:

include_label false
output_tag false

[repeatedly]

Sorry, I'm not sure what the PR cause.
Could you show me the actual output?
It seems TSV, right?

[kayrus]

So if you have the following json input:

{tag:'tag',key1:'val1',key2:'val2',key3:'val3'}
{tag:'tag',key1:'val4',key2:'val5',key3:'val6'}

The LTSV with the following options

include_label false
output_tag false
delimiter ' '

will provide output:

val1 val2 val3
val4 val5 val6

In some cases it is necessary to get plain values output instead of json.

[repeatedly]

It seems CSV family, not LTSV.
So adding CSV/TSV formatter is better than adding more parameters to LTSV.

[repeatedly]

#489 supports similar use-case.
So I close this PR. Please use above PR instead.