Sections 1 and 2

Section 1:
- inserted remark on equivalence relation on the index set after the
Lemma on the behaviour of the antipode on local units

End of Subsection 2.1:
- Moved definition of an invariant subspace, Lemma of Schur and the
direct sum construction there and showed that Corep(A) is abelian-

End of Subsection 2.2:
-  Added a Lemma on the decomposition of the trivial corepresentation
   into irreducible ones, outlined the notion of a partial tensor
   category,  sketched how the decomposition of the unit leads to
   such a partial  tensor category, and how one can form a total
   (non-unital)   tensor category. TO DO: Summarise what the
   decomposition of the tensor unit implies for Corep(A), i.e. natural
   decomposition of any corepresentation. This could, however, also be
   done more directly.
Merge branch 'master' of https://github.com/thomastimmermann/face-algebras-from-ergodic-actions-of-compact-quantum-groups