Geo-parameters

Added friction velocity:

gp.wind.FrictionVelocity (non-CF)
gp.wind.XFrictionVelocity (CF)
gp.wind.YFrictionVelocity (CF)
gp.wind.FrictionVelocityDir (non-CF)
gp.wind.FrictionVelocityDirTo (non-CF)

Also connected these as a family

find_me_in method now returns list

Fixed that empty family is now the empty dict, not None


>> gp.wave.Hs.my_family()
{}
>> gp.wave.Hs.my_family('x')
None

Periods and frequencies now have families, e.g.


>> gp.wave.Tp.i_am()
'period'

>> gp.wave.Tp.my_family().get('frequency')
<class 'geo_parameters.wave.Fp'>


Names in family has been changed to long names ('mag' -> 'magnitude'). All of them are now:

`'magnitude','direction', 'x','y','opposite_direction','period','frequency'`

`my_family()` method now also has a short way to get a family member:

`assert gp.wind.WindDir.my_family('magnitude') == gp.wind.WindDir.my_family().get('magnitude')`

We can now also find a parameter in a list of parameters:

`gp.wave.Hs.find_me_in([gp.wave.Hs, gp.wave.Tp])` -> `gp.wave.Hs`

It uses the `is_same()` method, so we can get a specific instance of a class using the class:

`swh = gp.wave.Hs("swh")`
`gp.wave.Hs.find_me_in([swh, 'hs'])` -> `swh`

The property `unit` was changed to units to match netcdf standards

The `is_same` method now returns false if no standard_name can be decoded (e.g. if a string is given)

Relationships have been added between parameters:


>> gp.wave.Hs.my_family()
None

>> gp.wind.XWind().my_family()
{'x': gp.wind.XWind, 'y': gp.wind.YWind, 'mag': gp.wind.Wind, 'dir': gp.wind.WindDir}



>> param = gp.wind.XWind

>> param.my_family().get("x")
gp.wind.XWind
>> param.my_family().get("y")
gp.wind.YWind
>> param.my_family().get("mag")
gp.wind.Wind
>> param.my_family().get("dir")
gp.wind.WindDir