Expand shared memory current deposition to Esirkepov

[hklion]

No description provided.

[hklion]

Inclusive timers for current deposition at [88579b0](https://github.com/atmyers/WarpX/pull/2/commits/88579b09e5a08cb6500f209d63e825a9ef373198) on 8 GPUs on crusher.

2-2-2_esirkepov   10.34
2-2-4_esirkepov   6.235
2-2-8_esirkepov   4.635
4-4-4_esirkepov    3.93
4-4-8_esirkepov   4.526
8-8-8_esirkepov   6.742
devel_esirkepov   4.633

2-2-2_direct      2.843
2-2-4_direct      2.122
2-2-8_direct      1.922
4-4-4_direct      1.607
4-4-8_direct      1.643
8-8-8_direct      1.952
devel_direct      4.822

64 threads per block

2-2-2_esirkepov    7.251
2-2-4_esirkepov    5.746
2-2-8_esirkepov    5.509
4-4-4_esirkepov    5.355
4-4-8_esirkepov    6.607
8-8-8_esirkepov    11.03

256 threads per block

2_2_2_esirkepov    12.92
2_2_4_esirkepov    7.811
2_2_6_esirkepov    6.005
2_2_8_esirkepov    5.138

4_4_2_esirkepov    5.149
4_4_4_esirkepov    3.828
4_4_6_esirkepov    3.446
4_4_8_esirkepov    3.226

6_6_2_esirkepov    3.782
6_6_4_esirkepov    3.216
6_6_6_esirkepov    3.024
6_6_8_esirkepov    3.313

8_8_2_esirkepov    3.212
8_8_4_esirkepov    3.012
8_8_6_esirkepov    3.254
8_8_8_esirkepov    3.232