correcting the amount of data per step in v11 Density_PAR?

Thanks to Ibon for finding this

we do not support python 2 anymore

bumped version to 2.5.0

a lot of blank except: were replaced,
maybe some of them incorrectly

ess.lib_tw is broken due to removing star imports

Update SP_Relativity.py with functions emit_geo and emit_norm which return the geometrical and normalized emittances

bump version to 2.3

and a little import cleaning

renamed fieldmapy -> fieldmap
split out example for fieldmap, added map files for testing
some minor  modifications of the functions

using meshgrid for the data
added interpolation function

moving examples out of sources

added files: fieldmapy.py: has several functions which are useful for manipulating the data for TraceWin fieldmaps
                   SP_Relativity: has several function which return relativistic beta and gamma from energy and vice versa
		    TTF.py: has few functions for calculating TTF of cavity fieldmaps
added example: Scan_Energy_gain_in_fieldmap-v16.pynb which has several functions and examples for phase scan (to be completed)