NITerAPI: modify func sign_in() in User.py

improve sign_in(), save time and money
NITerAPI: add API_DB and API_TABLE

DateBridge.py:
    bug fix: func select()
    bug fix: var db of class LongtimeDB

Config.py:
    bug fix: var DB_NEME
    add var TB_NEME
NITServer: update /showpwd

using new DB in DataBridge