Fix problem with the UI in workflow_viewer
 Code cleanup (run_* scripts)
 Fix problem with Optic output/log files
 Fix problem with run_qptdmscr.py
 Helper function for the definition of the k-point samplng, LDA+U, LEXX.
 Doc cleanup
 Add new examples for LDA+U, MgB2 and bands with frozen phonon at q=0.
 Remove sudo from pip commands.
 Avoid installing numpy as scipy with pip (use apt-get)
 Remove iround
 Require pymatgen2.8.7
 Move imports from abipy.__init__.py to abipy.abilab.
 Upgrade requirements.
 Fix regression in GUI demo
 Add pseudos for Mg and B
 Add new example with ferromagnetic Fe.
 Bypass a bug in matplotlib (grid of plots with nplots % 2 != 0)
 Remove gui/__init__.py before running nosetests with Travis.
 Unit tests for pickle serialization.
 Add /usr to LD_LIBRARY_PATH to solve netcdf4 issue