remove unused functions

- remove Variables.get_names(), .get_nodes_of_global_dofs()
  Variable.is_non_state_field(), FieldVariable.get_global_node_tab()
update setting of variables data (use Variable.set_data())

- remove Variables.data_from_state()
- update Variables.set_data()
- rename/update Variables.non_state_data_from_state() -> .set_data_from_state()
- remove Variable.data_from_state(), .data_from_data()
- rename/update Variable.data_from_any() -> .set_data()
- rename FieldVariable.data_from_qp() -> .set_data_from_qp()
- update all depending code
fix ANSYSCDBMeshIO.read(), guess it with .inp suffix

- new .guess()
- for mixed element meshes and coordinates without "solid" keyword
allow quadratic elements in ANSYSCDBMeshIO.read(), strip extra nodes

- allow more format variants
- add remap argument to mesh_from_groups()
- add .dat suffix
fix smooth_mesh() - improve efficiency
docs: add support section to main page
script/save_basis.py: plot nodes of selected dofs

- new plot_nodes()
clean up sfepy/fem/parseReg.py
support nodes and elements of set in create_bnf()
update region_leaf() and test for "nodes of set" selector

- prepare for "elements of set" selector
- nodes of group support only int id
update ANSYSCDBMeshIO.read() to support nodes of boundary conditions
move bodies of functions for saving regions from ProblemDefinition to Domain

- new Domain.save_regions(), .save_regions_as_groups()
- update ProblemDefinition.save_regions(), .save_regions_as_groups()
clean up sfepy/fem/meshio.py
support node sets (nodes of boundary conditions) in HDF5MeshIO.read(), .write()
fix omitting nodes of boundary conditions in Mesh.write()

- add nodal_bcs argument to Mesh.from_data()
new get_face_areas() + test
script/convert_mesh.py: new --center option
new global option 'check_term_finiteness'
check finiteness in Term.evaluate()
clean up sfepy/fem/domain.py