file upload docs

docs/dcu-fileupload.md

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+# Data Controller for SAS: File Uploads
+
+Files can be uploaded via the Editor interface - first choose the library and table, then click "Upload".
+
+
+<img src="/img/dcu-files1.png" height="350" >
+
+The following should be considered when uploading data in this way:
+
+ - A header row (with variable names) is required
+ - Variable names must be the identical to the target (although this is not case sensitive)
+ - Duplicate variable names are not permitted
+ - Missing columns are not permitted
+ - Additional columns are ignored
+ - The order of variables does not matter
+ - The delimiter is extracted from the header row (so for `var1;var2;var3` the delimeter would be assumed to be a semicolon)
+
+When loading dates, be aware that the data controller makes use of the `ANYDTDTE` and `ANYDTDTTME` informats.
+This means that uploaded date / datetime values should be unambiguous (eg `01FEB1942` vs `01/02/42`) to avoid confusion - as the latter could be interpreted as `02JAN2042` depending on your locale and options `YEARCUTOFF` settings.