Improve bilevel particle advection

Opencl advection kernel modification for bilevel high order interpolation (commits 0e7efc09 and 78460030) was not fully correct and performant. These commits was inverted in the mpi-operator branch by commit 3a2d689d

TODO :

Implement a not full line cache for velocity bilinear interpolation (bilevel)
Implement a higher order interpolation for velocity in a separate operator
Add support for resolution larger than max dimension of a thread block.

Edited Sep 02, 2019 by EXT Jean-Matthieu Etancelin

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