Bumping gaia.json for 1 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/9a1b281413f6
Author: Julien Wajsberg <felash@gmail.com>
Desc: Bug 906316 - Don't download the xulrunner SDK each time we change a branch if their configuration are different (follow-up) r=etienne

Add the new directories to .gitignore