Fix parameter begin point on edge

See merge request gmsh/gmsh!52

Pointwise quality visualization

See merge request gmsh/gmsh!57

No need to create different pview for different element type as soon as same order. Better implementation pview of pointwise quality

- all functions now return a vector<int>
- first entry is the return code
- any integer output value is appended

This makes it as natural to use when specifying tags explicitly or when letting Gmsh return new ones