attached license text for pyAMG code
Merge pull request #1 from DiMoser/hotfix/license-note

attached license text for pyAMG code
Merge branch 'development' into feature/the-big-cleanup
Merge branch 'feature/the-big-cleanup' into feature/rewamping-multi-levels
multi_levels: some renames to shorten module names
levels: tweaking AbstractLevel and TimeLevel (also adjusted tests)
adding some basic custom ABCs

(similar to those defined by collections.abc)
Data Structures: AbstractSpatialObject and default Scalar1D
Data Structures: remove Comparable from AbstractSpatialObject
tests: adding tests for Scalar1D data structure
Merge branch 'feature/spatial-object' into feature/rewamping-multi-levels
Level Transitioners: AbstractLevelTransitioner + SpaceInvariantTimeTransitioner