start working on tao-in-petsc.
fix issues on enable_petsc_tao and updating demos and tests
remove FindTao cmake module
tiny fix
add Neumann and Dirichlet bcs to demo-dg-poisson
change n and h in Poisson.ufl
Fix doctest for mixed-poisson-dual.
Rename domain_data to subdomain_data everywhere.
Rename domain_type -> integral_type everywhere.
Merge branch 'martinal/topic-fix-mixed-poisson-dual-doctest'
Fix Issue 274.
Minor changes.
Merge branch 'mirok/fix-issue-271'
Merge branch 'garth/fix-issue-274'
Merge branch 'martinal/topic-rename-domain_id-and-domain_data-and-domain_type'
Some fixes for 64-bit PETSc.
Merge branch 'cmaurini/tao-in-petsc'
Merge branch 'garth/fixes-for-petsc-64'
Merge branch 'master' into garth/fix-issue-287

Conflicts:
	CMakeLists.txt