add readme with instructions for generate csv file from Excel

@netcdf_native/Readme_tsgqc_netcdf.txt

+Instruction for tsgqc_netcdf.csv file generation
+
+Edit or modify tsgqc_netcdf.xls file with Excel. In the column dimension,
+     check that each cell as simple parenthesis, use 'collage speciale'
+     to do it
+
+     Load Excel file in memory and write it csv
+
+>> d = dynaload('tsgqc_netcdf.xls')
+dynaload
+
+	file:     'C:\svn\tsg-qc\trunk\@netcdf_native\tsgqc_netcdf.xls'
+
+	DIMENSIONS               	 9 [hashtable]
+	VARIABLES                	68 [hashtable]
+	ATTRIBUTES               	36 [hashtable]
+	QUALITY                  	10 [hashtable]
+
+list of methods
+>> write(d,'tsgqc_netcdf.csv')
+Write data file:   C:\svn\tsg-qc\trunk\@netcdf_native\tsgqc_netcdf.csv
+