BOUT++ v4.1.2

This is a bug-fix release, fixing the following issues in BOUT++:

• Updates to the documentation
• Added missing __setitem__ and keys functions to python Datafile
• Fixed INVERT_KX_ZERO in serial_tri Laplace solver
• Fixed incorrect number of guard cells in serial_tri Laplace solver
• Fixed Laplacexy examples
• Fixed bug in calculation of non-uniform correction
• Disabled plotting of test-fci-slab when running the integrated tests
• Fixed bug during configure if NetCDF not found
• Fixed typo in bout-runners example input file