Replace the TRT_Cabling package by a CondAlg and an accessor tool.

Although the TRT cabling map is static and does not depend on the event, it is considered preferable to store it with a CondAlg and access it with ReadCondHandle. This required a major rearrangement of the TRT_Cabling package. At the same time a lot of legacy code, used for pre-Run1 cabling scenarios, has been removed. Unfortunately, a const_cast could not be avoided. At the root of this problem is a small private function TRT_CablingData::idandhash_t& find_idandhash (int rod, int bufferPosition) that I could not make const after many tries.