Analyses sorted by priority in Add Analyses view and preserve AR order when adding into Worksheet

[xispa]

Fixes #303

IMPORTANT: Requires the execution of upgrade step v1.1.1

In Analyses Add View (when creating a Worksheet), the analyses were displayed randomly. After their selection (and addition into a new Worksheet), the position of the Analysis Requests in the Worksheet was the same as the Analyses Add view, random.

With this Pull Request, the Analyses in Add Analyses view are sorted by priority by default (from more priority to less priority), at the same time that preserves the correct order of analyses in accordance with the SortKey value as defined in the Analysis Service (#331):

When selected and submitted, the order of the Analysis Requests inside the Worksheet is corrected, so the ARs are sorted in natural order of creation, but again, keeping the Analyses' SortKey order:

Note the priority of AP-0010-R01 was "High" and the priority of "AP-0005-R01" was medium, so:
a) In Add Analyses view, AP-0010-R01 is displayed before AP-0005-R01
b) In Worksheet manage results, AP-0010-R01 is displayed after AP-0005-R01
c) In both cases, analyses are sorted in accordance with their SortKey value (Iron = 20, Calcium = 50, Magnesium = 70, Copper and others = Not defined)

[ramonski]

Just a little style issue here to remove code complexity.

Better do something like this:

analysis_request = self.getRequest()
if analysis_request is None:
    return None
# continue with the rest of the code with a lower indendation level
ar_sort_key = analysis_request.getPrioritySortkey()
...