Builder objects should have sort key member

[YngveNPettersen]

I am presently updating our buildbot version to 3.11, and I am transferring our angularJS patches to react.

While doing that I discovered that, apparently, the <td key=foo> sort key does not work, the entries in e.g. the builders list are displayed in the sequence they were retrieved from the DB (which appears to be alphabetic).

We have a code segment in www/react-base/src/components/BuildersTable/BuildersTable.tsx that creates a sort key based on what type of builder category the builder is, e.g. normal builders in one section, testers in another, official builders in a third. Inserting this information into the key element does not work. My guess is that something is missing in the react code setting up the table.

However, there is no reason that the sort key should be recalculated every time the table is generated. It should be possible to add it to the builder object when they are created during the buildbot.tac configuration step, with the builder name being the default.