devnet-v2.3

Security update

• add whitelist for dashboard static files to http server, prevents directory traversal attack on pythd dashboard

Functional updates

• poll program accounts
• Fix constructor parameter order and unnecessary declaration.
• Add ability to send price updates without pyth_tx.
• pyth.cpp: add upd_price_val for explicit price value updates (#32)
• [pythd] Update user::parse_get_product code.
• pythd: Add get_product and get_all_products WS methods.
• fix uninit variable