Document all FIX Session settings

Answering a question posted on the mailing list I found at least one undocumented setting:

• The TestRequestDelayMultiplier is not documented.

So we should document it and at the same time check for other undocumented features.
Here is the list of all session setttings (defined as constant with the prefix "SETTING_" in the Session class) which are
not mentioned in the "configuration.html":

• TestRequestDelayMultiplier
• NonStopSession
• DisableHeartBeatCheck
• ForceResendWhenCorruptedStore
• AllowedRemoteAddresses

Steps

• Added documentation for missing items.
• Corrected formatting:
• Some settings are not in italics.
• Always "Y<BR>N".