Fix several issues for Linux around casting SDKManager to concrete class: mostly with reading devices.xml which Unix does not support. Migrated ISDKManager#getMinimumSupportedSBSv2Version() to API. Can now import and create Symbian projects.

<?xml version="1.0" encoding="UTF-8"?>
<projectDescription>
	<name>com.nokia.carbide.search.system-feature</name>
	<comment></comment>
	<projects>
	</projects>
	<buildSpec>
	</buildSpec>
	<natures>
	</natures>
</projectDescription>