ENH: viz: different threshold in 2D and 3D
ENH: viz: different threshold in 2D and 3D

Add the possibility of having different thresholds for 2D and 3D plots

alexis-roche/register,bthirion/nipy,arokem/nipy,bthirion/nipy,alexis-roche/niseg,alexis-roche/nipy,nipy/nireg,alexis-roche/nireg,alexis-roche/nipy,arokem/nipy,alexis-roche/nireg,bthirion/nipy,alexis-roche/register,alexis-roche/nipy,alexis-roche/register,alexis-roche/niseg,alexis-roche/nipy,arokem/nipy,bthirion/nipy,nipy/nipy-labs,nipy/nireg,arokem/nipy,nipy/nipy-labs