Demo jupyter notebooks

[TomasKulhanek]

Create interactive demo notebooks following examples in documentation so the user can directly launch, manipulate and experimentate.

• new directory /notebooks with files - demo-[x]-[name].ipynb
• Preprocessing
• Reconstruction
• Regularisation

[TomasKulhanek]

notebooks established and first demo submitted - other demo might be created on demand or from existing resources sparsed among different ccpi related components.

[TomasKulhanek]

Regularization demo created in Octave. However Octave build from conda-forge seems not to support imread(). Filled issue conda-forge/octave-feedstock#18
and pull request to fix it in conda-forge conda-forge/octave-feedstock#19