* new functions: mesh/addHomologyRequest, mesh/clearHomologyRequests
    * changed argument of mesh/computeHomology + removed mesh/computeCohomology

- new optional arguments to model/addPhysicalGroup so that one can name a group at the time of creation

- pass optional dimTags to mesh/removeDuplicateNodes so we can merge nodes on parts of models

tutorial/ -> tutorials/

in addition to the default camelCase function names, add snake case aliases in the Python and Julia API, as this is the recommended style in these languages

initializing the api now sets General.Terminal=1 (to print messages by default) and General.AbortOnError=2 (to throw an exception as soon as an error happens) - cf. #1043

fix gmsh.option.setString("Mesh.MshFileVersion", "x.y") -> gmsh.option.setNumber("Mesh.MshFileVersion", x) (cf. #914)

changed API for creation of simple entities: the tag is now optional, and provided at the end (with default value = -1)

removed gmshModelGetVertexCoordinates (not necessary) + return parametric coords in gmshModelGetMeshVertices