[yaspgrid] add EntitySeed default constructor and method isValid
[onedgrid] add EntitySeed default constructor and method isValid
[albertagrid] add EntitySeed default constructor and method isValid
[uggrid] add EntitySeed default constructor and method isValid
[alugrid] add EntitySeed default constructor and method isValid
[geometrygrid] add EntitySeed default constructor and method isValid
[bugfix][test] fix assertion for entityseed test

we checked the wrong seed for validity
[bugfix][sgrid] fix EntitySeed::isValid

we had it the wrong way around
[bigfix][albertagrid] fix isValid() implementation