VarEntry/valueOf(Object)

multi-purpose Object->VarEntry converter
(minor)(refactoring)KStringTest/callInstance

use VarEntry.valueOf() instead of interpreting args[i] inline.
KString/create/substring/concat & Test
add KStringTest to AllTests
Elimination of unnecessary appearances of "KVMObject"

In almost all classes, objects in KVM must be handled as addresses(or VarEntry's representing them)
KString fix

static-call
explanations of methods provided in String