Bug 1115066 - Thunderbird start page: add redirects for locales

Locales: ca, cs, de, es-ES, fr, fy-NL, gd, hr, hy-AM, it, nl, pt-BR, sk, sl, sq, uk, zh-TW.
Merge pull request #2611 from flodolo/tb_locales

Bug 1115066 - Thunderbird start page: add redirect to Bedrock for locales