Geometry and configuration of Magnetic Field from DB

Infrastructure to take the MF geometry and configuration from DB instead than from python cfg. 
Changes include:
- Specific record for MF geometry (MFGeometryFileRcd), do not use GeometryFileRcd anymore. 
- New DB payload for MF configuration (MagFieldConfig); incl. record, tools to create it, etc.
- Prototype of new ESProducer to use the above (no change in behaviour for existing producers)
- Some refactoring in MagneticField to allow construction of parametrized fields at runtime
- removal of one large reference file as reuested by Slava (cf #5269)

This PR introduces no change in standard configurations (regression tested). Plan to switch to the new mechanism in a future PR, once the DB is populated with the new payloads.

Relevant Discussion:
https://indico.cern.ch/event/328166/session/1/contribution/24
```LCGReflex/std::pair<std::basic_string<char>,int>```
shows up twice after this got merged in the following
```
   **pluginCondFormatsMFObjectsCapabilities.so**
   **pluginDataFormatsStdDictionariesCapabilities.so**

```

check with 
```duplicateReflexLibrarySearch.py  --edmFile $CMSSW_BASE/lib/$SCRAM_ARCH/.edmplugincache --edmPD```

all the local library definitions should be moved to the StdDictionaries