Name collision in `d2q9_npe_guo` model

[kubagalecki]

phi0 density collides with phi0 setting:

TCLB/models/electrokinetic/d2q9_npe_guo/Dynamics.R

Line 2 in d66b8b3

AddDensity( name="phi[0]", dx= 0, dy= 0, group="phi")

TCLB/models/electrokinetic/d2q9_npe_guo/Dynamics.R

Line 103 in d66b8b3

AddSetting(name="phi0", unit="V", default=1., comment='')