Make subject line of contribute email for end-users localizable.

Keep the existing filterable subject lines for Mozilla contacts.
Fixes 854992
Fix Bug 962061 - Fix the footer RTL layout (language switcher: ltr direction is hard-coded)
Fix Bug 977355 - broken link to superheroes wanted on mozilla.org/contribute
Merge pull request #1738 from kyoshino/bug-977355-tb-support-links

Fix Bug 977355 - broken link to superheroes wanted on mozilla.org/contribute
Merge pull request #1606 from kyoshino/bug-962061-footer-rtl

Fix Bug 962061 - Fix the footer RTL layout (language switcher: ltr direction is hard-coded)
Merge pull request #1588 from 6a68/bug-854992-localize-contribute-email-subject-line

Bug 854992 Make subject line of contribute email for end-users localizable.