all: remove theory import path references

In Isabelle2020, when isabelle jedit is started without a session
context, e.g. `isabelle jedit -l ASpec`, theory imports with path
references cause the isabelle process to hang.

Since sessions now declare directories, Isabelle can find those files
without path reference and we therefore remove all such path references
from import statements. With this, `jedit` and `build` should work with
and without explicit session context as before.

Signed-off-by: Gerwin Klein <gerwin.klein@data61.csiro.au>

licenses: convert license tags to SPDX

Isabelle2018: new "op x" syntax; now is "(x)"

(result of "isabelle update_op -m <dir>")

Initial proof updates for combinator changes.

Removes all trailing whitespaces

wp_cleanup: update proofs for new wp behaviour

The things that usually go wrong:
- wp fall through: add +, e.g.
apply (wp select_wp) -> apply (wp select_wp)+

- precondition: you can remove most hoare_pre, but wpc still needs it, and
sometimes the wp instance relies on being able to fit a rule to the
current non-schematic precondition. In that case, use "including no_pre"
to switch off the automatic hoare_pre application.

- very rarely there is a schematic postcondition that interferes with the
new trivial cleanup rules, because the rest of the script assumes some
specific state afterwards (shouldn't happen in a reasonable proof, but
not all proofs are reasonable..). In that case, (wp_once ...)+ should
emulate the old behaviour precisely.

lib/spec/proof/tools: fix word change fallout

some of the global Isabelle2014 renames

option_case -> case_option
sum_case -> case_sum
prod_case -> case_prod
Option.set -> set_option
Option.map -> map_option
option_rel -> rel_option
list_all2_def -> list_all2_iff
map.simps -> list.map
tl.simps -> list.sel(2-3)
the.simps -> option.sel

Import release snapshot.