adding new OH component

not fully functioning yet
updates to gitnore

deleted VS files
added N2O emis to concentrations
more changes to n2o/ch4/oh/o3
n2o
Working N2O component

converts from emissions to concentrations
changes to initial lifetime
Merge branch 'ch4/n2o'

Conflicts:
	project_files/visual_studio/hector/hector.sdf
	project_files/visual_studio/hector/hector.suo