Handle large CSV file sizes for upload

[Floppy]

We can't validate anything over 700k in a file upload without causing an error (see https://github.com/theodi/csvlint/issues/201). It's unclear whether this is because of the nginx file upload size limit, or something in the app instead.

We want:

• validation of web-hosted CSVs of any size
• validation of uploaded files of up to 100MB size
• [x] Work out where the bottleneck is
• [x] Increase the nginx file size limit anyway to 100M (see https://github.com/theodi/csvlint/issues/201)
• [x] Make sure that the app can handle those file sizes (locally, without nginx involved). See https://github.com/theodi/csvlint/issues/213 for possible thoughts on how this could be achieved in a user-friendly way.

[Floppy]

@bcouston and @quadrophobiac are going to take a look at this to see if we can make some progress before CSVlint is used for the DaPaaS workshops next week, or at least isolate the problem further.

[bcouston]

@Floppy This might be server side, locally I can validate a 1.2MB csv file (http://training.theodi.org/resources/dataset2.csv), on live, 413 entity too large error with an infinite validation loop.

[bcouston]

On the local side, Mongo can't store files larger than 16MB, investigating into using a package that splits data into chunks (http://www.resumablejs.com/) or GridFS.

[bcouston]

The error

[dicknorris]

Book to DaPaaS > WP1 > Task 1.2

[Floppy]

The server-side and investigative stuff here is OK, and the next thing is to look at how we make a better upload experience for people using a javascript uploader like ResumableJS.