Use correct variable name for auto-install page (bug 1063170)

Technically not related to the referenced bug, but I found the issue
while working on the referenced bug so there you go.
Add static page for use in addon-install snippet (bug 1063170).
Merge pull request #276 from Osmose/snippet-lastpass

Bug 1063170: Add static HTML page for addon-installing snippet
Commit from Mozilla Verbatim by user steekid.: 3015 of 3015 strings translated (0 fuzzy).