Adds allocation breakdown for each portfolio under All portfolios

[clsacramento]

I originally tried out the fava-portfolio-summary extension because I was looking for a simple way to track my stock allocation versus the rest of my portfolio. While associating different accounts to my stocks portfolio, fava-portfolio-summary will show me the percentage of each security under this portfolio but not the percentage of stocks in the whole portfolio. This PR adds this as part of the summary, on the top under All portifolios.

For example, this is how it looks for me with this change: https://paste.pics/GPRDG

[PhracturedBlue]

This seems ok at the 1st level, but when I descend into the 2nd level, the allocation percentages aren't correct. Specifically, I expect each line item to be a percentage of he whole, not the percentage of its parent. For instance in the image below, row 5 should be 15.33% (34.05%*45.01%) instead of 45.01%

[clsacramento]

Oh yeah, you are right! Sorry for that, actually I should have set to None the children for each portfolio summary line since the goal is not to exapnd them as they are already broke down later under portfolios.

[clsacramento]

Ops sorry for the sending to new commits. I had cleared up my dev environment the other day and didn't have an easy way to test the change without pushing to my branch.

Can you please take a look now? If the latest commit the lines under All portfolios are not expandable so we just have the allocation per portfolio versus Total.

The details of each portfolio are then broke down with the tables for each portfolio as you already had before. WDYT?