Set up Prices screen; Add price subscription code;

ADDED: CustomConfig.cs;
 - To load appSettingsPrices variables and make them globally available
ADDED: CustomContainers.cs;
 - To provide DictionaryOfHashSet<>
ADDED: SecDefn.cs;
 - To provide dictionary data for front end, subset of MarketDefn
ADDED: SubscriptionManager.cs;
 - Handles subscription duties.
CHANGED: Snapshot.cs;
 - Added JSONSerialize() fn to convert snapshot to JSON format
CHANGED: Market.cs;
 - Applies lock before returning Snapshot.
 - Price() returns bool; true if price string has actually changed.
CHANGED: MarketManager.cs;
 - Fns now lock before access variables.
 - Now does not load, match or consume orders if not running.
 - Added GetTradableContracts() to provide contract list to front end.
 - Added getMarkets() to copy the data rather than lock it open.
 - Removed GetSnapshots as part of SubscriptionManager re-think.
CHANGED: BaseDAL.cs, MarketDefnDAL.cs, MarketPriceHistoryDAL.cs, OrderQInDAL.cs, PositionDAL.cs, PositionLimitDAL.cs, WorkingOrderDAL.cs
 - Exits if MarketManager is not running.
CHANGED: AsyncHttpHandlerPrices.cs;
 - Removed static ctor code, moved to CustomConfig class.
 - Removed local config variables, replaced by CustomConfigs.
 - Changed inbound message processor to call SubscriptionManager fn
 -   and to use Int64 in the dictionary argument.
CHANGED: AppSettingsPrices.Web.Config;
 - Added all the data for the pricing screen creation.
CHANGED: Trading.css;
 - Styles for table creation for pricing screens etc.
CHANGED: FCUtils.js;
 - Added isEmptyObject() test function.
CHANGED: Prices.js;
 - Added virtually all original MiniMkt02 pricing code.
CHANGED: Trading.aspx / Trading.aspx.cs
 - Added pricing screen and table defn code.
CHANGED: Web.Config
 - Added price table column definitions etc.