Improve SBG exception message

[vmutafov]

Currently, the SBG will fail when it couldn't find a class. This is OK, but the error message should say which class was not found:
java.lang.RuntimeException: Class not found! at org.nativescript.staticbindinggenerator.generating.parsing.classes.hierarchy.generics.impl.GenericsAwareClassHierarchyParserImpl.getJavaClassFromCache(GenericsAwareClassHierarchyParserImpl.java:320) at org.nativescript.staticbindinggenerator.generating.parsing.classes.hierarchy.generics.impl.GenericsAwareClassHierarchyParserImpl.getClassHierarchyRecursively(GenericsAwareClassHierarchyParserImpl.java:137)

[vmutafov]

#1401