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

validated on https://icalendar.org/validator.html

bump version to 2.3

(that does not work particularly well)

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)

SP_relativity and TTF added. They contain sets of functions to calculate beta, gamma and energy from each other and calculating the TTF and input phase for max energy gain in a field map.