CSV importer fixes

Features
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* Catching field errors so we can pass a more descriptive error to the user
* Allowing location__name to filter field for SystemRacks.
* CSS animation during CSV processing
* Green gradient added to new fields

BUGS
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* Renamed _get_dict_related and _get_pk_related to get_realted_from_dict and get_related_from_pk. These names seem more accurate.
* Renamed header to raw_header. raw_header is more accurate since it hasn't been parsed yet.
* system_model should have been server_model
* ServerModel should have been Allocation
* Make sure all examples in the documentation worked
* Fixed white space trimming around headers
Using classes DoesNotExist instead of general Exception
Cleaned up some code

Removed silly attempt to detect errors in html and used status kwarg in render instead. Using the test client now so templates are rendered (in case there are jinja2 errors).

Did some other things for readability.