Downloads: Correct sheet order
Downloads: Correct sheet order

Problem:
In the downloads for XLS, XLSX and ODS the "Query" is the first
sheet, "Results" the second. This is confusing.

Root cause:
When constructing the `pyexcel.Book` a `dict` is provided with
the required sheets. A dict is unordered, as as result, the
Sheets are added in alphabetical order to the Book.

Solution:
Use an OrderedDict, so the correct ordering is maintained.

beancount/fava,corani/beancount-web,aumayr/beancount-web,corani/beancount-web,yagebu/fava,corani/beancount-web,aumayr/beancount-web,yagebu/fava,beancount/fava,yagebu/fava,aumayr/beancount-web,yagebu/fava,aumayr/beancount-web,beancount/fava,yagebu/fava,beancount/fava,corani/beancount-web,beancount/fava