Added use fast yaml loader option

[JeanLucPons]

This PR adds an option to use fast yaml loader:

#        use_fast_loader : bool
#            Use fast yaml loader. When specified, no line number are reported in case of error, 
#           only the element name that triggered the error will be reported in the exception)
sr = Accelerator.load("tests/config/EBSOrbit.yaml",use_fast_loader=True)

[gubaidulinvadim]

For me, this is good. It passes all the tests. The only thing I do not understand is if we have a fast c-loader, what is the point of having a slow loader (and the slow one being the default option)?

[JeanLucPons]

For me, this is good. It passes all the tests. The only thing I do not understand is if we have a fast c-loader, what is the point of having a slow loader (and the slow one being the default option)?

As mentioned in the doc, the slow loader prevents to get the line number informations.

Using Fast loader:

pyaml.common.exception.PyAMLConfigException: 'powerconverters': Field required, 'powerconvertes': Extra inputs are not permitted,  for object: 'pyaml.magnet.linear_cfm_model' 

Using slow loader:

pyaml.common.exception.PyAMLConfigException: 'powerconverters': Field required, 'powerconvertes': Extra inputs are not permitted /home/esrf/pons/pyaml/tests/config/EBSOrbit.yaml at line 4739, colum 7,  for object: 'pyaml.magnet.linear_cfm_model' /home/esrf/pons/pyaml/tests/config/EBSOrbit.yaml at line 4724, column 5.

A possible hack for this is to use by default the fast loader and if an errors occurs then reparse using the slow loader.