Finished code for global HLT trigger and the trigger menu implementation.

Finished code for global HLT trigger and the trigger menu implementation.
The HLT global trigger component now auto generates a AliHLTGlobalTrigger implementation on the fly from the trigger menu. This auto generated class performs the actual
trigger logic required.
Removed the readout list (which is a subset of a trigger domain) from the AliHLTTriggerDomain.
An AliHLTReadoutList class can now be auto generated from the trigger domain through the typecast operator.
Adding a simple TriggerConfig.C macro which is used to test the global trigger component via testGlobalTriggerComponent.C.
The AliHLTGlobalTriggerConfig class is added for use in trigger configuration macros such as TriggerConfig.C. This class makes it more user friendly to define a global HLT
trigger configuration and pass it to AliHLTGlobalTriggerComponent.
Also added AliHLTTriggerMenuSymbol and a list of symbols to AliHLTTriggerMenu so that variables can be defined, filled from input TObjects and used in global HLT trigger
expressions easily.