Changes to IM Logging, includes preference changes

indra/newview/app_settings/settings.xml

indra/newview/app_settings/settings_per_account.xml

indra/newview/llfloaterchat.cpp

indra/newview/llfloaterchat.h

indra/newview/llfloaterpreference.cpp

indra/newview/llfloaterpreference.h

indra/newview/llimview.cpp

indra/newview/lllogchat.cpp

indra/newview/skins/default/xui/en/menu_viewer.xml

...ewview/skins/default/xui/en/panel_preferences_privacy.xml