Separate the computation of hneigh into another kernel

Simplify the main GPU kernel and add another kernel 'k_pair_reneigh'. It works good on GTX1070 (Pascal), but still there is a problem with non-deterministic results on Volta.

I reimplement BaseCharge::compute methods in the child class LJ_TIP4PLong to correctly embed a new kernel in the code.

Also commit includes some codestyle fixes.