finalTestGrad=None even when warnflag=1
plan to add append() to both obs classes
plan to add cut() to twObs
implemented __add__ to StaticObs + removed order

It is important  not to sort coord because of the metric information linked to that specific order.
__add__ to TimeWindowObs

Alse removed isGridded from StatObs (served no purpose)
 added .cut() to TWObs
observations.__add__ when nObs==0
checkNan added to jTerm.gradTest
gradTest check for first 0.9w
minor modif
MAJOR bug solved: std vs variance in B_sqrt
for precondJTerms, final gradTest made with xOpt<>analysis!
removed finalTestGrad, findFirst9 by default
modified precondJTerm for optional final test
added errStr_isoHomo for coherent stats error production
bkgSig optional in errStr_isoHomo
new source: errorStruct
output format for gradTest
extracted opH_Adjoint from _gradCostFunc
In the middle of something:

Found a potential explanation for failed gradTest:
innovation calculated with full nonlinear model.
Changed the structure of TLMLauncher and Launcher to
adress this...
pyfKdV:branch uniformProp

in the middle of that...  the code should not work.