Japan's inbound tourism growth boosts retailers, railroad operators

* Yen at 7-year low pushes foreign tourist numbers to record high * Tourism and related stocks gain on surge in tourist spending * Railways, resort operators, retailers the main beneficiaries * Foreign tourist numbers expected to keep on rising By Ayai Tomisawa TOKYO, Dec 15 (Reuters) - Investors are snapping up Japanese stocks in the retail and transportation sectors, thanks to a weaker yen that has lured a record number of foreign visitors in one of the few bright spots fo