first implementation of a 3D grid search
adapt searchGrid to new gridSearch3
set dimnames of grid search results
adapt getBestGridParams to gridSearch3
bump version to 1.7.4 and introducing ImDiff field to synapter class
set ImDiff by setBestGridParams
add {set,get}ImDiff
adapt findEMRTs
remove searchGrid2
fix rownames order
fix spelling
adapt plotGrid
adapt plotFeatures(..., what = all) to 3D grid search
test for imthreshold == Inf
export {set,get}ImDiff
add documentation for {set,get}ImDiff
update plotGrid/plotFeatures documentation
turn warning about missing ion mobility into a message
update NEWS entries
Merge branch 'master' into 3DgridSearch

Conflicts:
	DESCRIPTION
	NEWS