licenses: convert license tags to SPDX

abstract: use new invocation label enum

globally use session-qualified imports; add Lib session

Session-qualified imports will be required for Isabelle2018 and help clarify
the structure of sessions in the build tree.

This commit mainly adds a new set of sessions for lib/, including a Lib
session that includes most theories in lib/ and a few separate sessions for
parts that have dependencies beyond CParser or are separate AFP sessions.
The group "lib" collects all lib/ sessions.

As a consequence, other theories should use lib/ theories by session name,
not by path, which in turns means spec and proof sessions should also refer
to each other by session name, not path, to avoid duplicate theory errors in
theory merges later.

Removes all trailing whitespaces

arch_split: More namespacing progress and invariant splitting. Checks halfway into Invariants_AI

arch_split: progress on namespacing abstract spec

paramatrised abstract and haskell specs over L4V_ARCH

Haskell translator was modified to support multiple translations
of the haskell, with different build parameters.