Merge pull request #52 from robertbachmann/code_cleanup

Code cleanup
Return SW_COMMAND_NOT_ALLOWED if no applet is selected
Replace duplicated javadoc with @see
Add javadoc to ApduCase, ByteUtil, and AIDUtil
Document applets, migrate to CLA=0x80
Add CLEAR_ON_* support
Make Card#disconnect(true) perform a reset
Check preconditons in APDU.getCurrent()

Make APDU.getCurrent() throw a SecurityExecption if
not called (directly or indirectly) from Applet#process(APDU)
Add AIDUtil#select()
Fix javadoc typos
Refactor exceptions thrown by Simulator