[map] Added icon overlay support using Nokia engine

[map] Added icon overlay support using Nokia engine

* Only icon support added
* Code modified to use overlay only if provided by engine
* Previous functionality has been retained
* Group overlay support using Nokia engine will be added next
* [Patch2] Handling overlays in group scenarios
* [Patch2] Issue fixes related to stray evas objects displayed
* [Patch2] Currently the Nokia overlay support is disable, to enable set ENABLE_MAP_ENGINE_OVERLAYS to true and compile
* [Patch3] Fixed incomplete merge from the earlier commit

Change-Id: I472490e1f65ddd8fdbcf1827eeed68b22568890d