Add extended checkbox to downloads

[mdoering]

For Coldp & Dwca the API offers now a simple download with just very few columns in a single CSV:

col:ID col:parentID col:status col:rank col:scientificName col:authorship

It is set as the default to avoid heavy, undesired downloads with all extensions.
To request a complete ywca or coldp archive one has to submit extended=true now in the request object.

Consider how to best offer this in the UI:

1. show new simple checkbox which is only active/shown for dwca & cold
2. offer 2 new formats (cold & ywca simple), maybe removing the ACEF one which we don't want to promote to save space

[mdoering]

making this high priority as the API defaults to simple and you cannot download a full ColDP from the UI any more