[perf] minimize ExternalContext.getInitParameter invocations in myfaces API

init-param from webapp context cannot change - it is sufficient read it once in constructor (ApplicationImpl for example)

New problem (new in 2.1) is "great" javax.faces.HONOR_CURRENT_COMPONENT_ATTRIBUTES param for pushComponentToEL and popComponentFromEL - at least we can cache it in component (because push and pop are called more then ones during one lifecycle) and maybe cache it's value also in org.apache.myfaces.context.servlet.ServletExternalContextImplBase.getInitParameter(String)

I have about ~ 90 000 invocations of getInitPaparameter in my test case in one request/response and that is not cheap.