tested areEqualDeep for arrays with nulls
refactored and tested isAssignableTo->canAssign
tested canReturn
tested canThrow
inlined couldReturn
tested zeroOrNull
extracted canInvoke from Invocation
tested and refactored Classes commons
made Invocation throw ProxyException
made invoke(Invocation) throw ProxyException
made Typing throw ProxyException
extracted ProxyException.check(boolean)
made proxy package throw ProxyException