* renamed private members for more clear code
* registerExternalBufferID() method to obtain unique ID for withExternalBuffer()
* PICoutManipulators::PICoutStdStream enum for select stream (stdout or stderr)
* Constructors now accept optional stream
* piCerr and piCerrObj macros
PIDir::temporary() moved to "mkdtemp"
PILog:
* now 4 levels
* you can set max level
* Error writes to piCerr
