initialisation to separate files
WIM2d.m code initial version

- running without crashing
- no breaking or wave advection -> debug
rename files, add boundary condition

- rename to be consistent with matlab code
- add boundary condition to pad_var routine so advected solution can be
periodic in y direction only
advection boundary conditions added

- periodic in x,y added
- periodic in y only added
WIM2d running without attenuation

- attenuation crashing for some reason
WIM2d has attenuation now.
redefine dimensions of directional spectrum

Move integration over direction to adv_atten_timestep_simple.m