sweq_partition: SWEQ partition for the block-LEnKPF
In robertsy/assimilr: Local Ensemble Kalman Particle Filters

Partition the observations in blocks for assimilation with block-LEnKPF. Takes into account the sweq geometry We assume that R is diagonal and don't take it into account

1	sweq_partition(H, taper, block.size)

`H`	the observation operator
`taper`	the tapering matrix (qxq)
`block.size`	chunk size in domain space to take into account for one block

ndim <- 168
## observe all rain + some wind:
y.ind <- c( (ndim+1):(ndim+10), (2*ndim+1):(3*ndim) )
H <- diag(ndim*3)[y.ind, ]
taper <- sweq_GC(ndim, 5)
partition <- sweq_partition(H, taper, 21)