Enhance the "MapTip" widget to disable/enable map tooltip

[hubu]

Currently in MapGuide, the client sends "QueryMapFeatures" request to get the tooltips every time we move the cursor. However, most of the requests are unnecessary and useless for the end-user. For example, when the user are doing measure/pan/zoom, the tooltips are redundant for the user. If we remove these unnecessary requests, we can reduce server's overload. This enhancement make the widget "Maptip" to be an button, so we can click it to enable\disable the map tooltips. Then the user has an opportunity to disable the map tooltip to reduce server's overload, and the user still can enable the tooltips again by press the button again. By default, the tooltip is enabled, so it won't affect the original users.

[hubu]

fix of this ticket