Core FileTag allows to write only XML or HTML content to file.
But there's a need to write flat content unix-like or in pseudo-xml (element collection without document root).
So FileTag must allow to write flat content to file.
Proposition to add a boolean "flat" property.
There also a need to add "append" property to.. append to existing file 
Improvement
Closed
Minor
FileTag must allow to append to flat file
