where条件，目前只支持单一的term匹配

[steden]

term只支持对keywords、数字类型的 == 条件。
参考.net的实现

  var time = "30";
  // Judgment time (with complex local function methods)
  TestContext.Data.User.Where(o => o.CreateAt >= DateTime.Now.AddMinutes(-time.ConvertType(0)).ToTimestamps()).ToList();
  // NETS native conditionals and self-resolving conditionals
  TestContext.Data.User
             .Where(q => q.Term(t => t.Age, 33))
             .Where(o => o.UserName.Contains("ste")).ToList();
  // Fuzzy Search and Positive Order Sorting
  TestContext.Data.User.Where(o => o.Desc.Contains("hello")).Asc(o => o.Age).ToList();
  // Prefix search and reverse sorting
  TestContext.Data.User.Where(o => o.Desc.StartsWith("hello")).Desc(o => o.Age).ToList();
  // Suffix search (only Keyword type is supported)
  TestContext.Data.User.Where(o => o.UserName.EndsWith("en")).ToList();
  // Not equal to a value
  TestContext.Data.User.Where(o => o.UserName != "aaa").ToList();
  // and operation, if two Where methods are called, is also equivalent to using and
  TestContext.Data.User.Where(o => o.UserName == "steden" && o.Age == 18).ToList();
  // or operation
  TestContext.Data.User.Where(o => o.UserName == "steden" || o.Age >= 10).ToList();