Convert license tags to SPDX identifiers

This commit also converts our own copyright headers to directly use
SPDX, but leaves all other copyright header intact, only adding the
SPDX ident. As far as possible this commit also merges multiple
Data61 copyright statements/headers into one for consistency.

manual: document badge range for 64-bit platforms

manual: ipc: clarify sending caps is a copy

SELFOUR-6: Add GrantReply to the rights system.

GrantReply is a new access right added to endpoint capabilities, which
allows seL4_Call to be used on those capabilities (specifically, it
allows reply caps *only* to be granted across endpoints).

Prior to the addition of GrantReply, endpoint capabilities required the
Grant access right, which allowed any arbitrary capabilitiy to be
transferred over an endpoint. Using GrantReply, systems can now be
constructed where threads using seL4_Call over an endpoint do not need to be in the same
security subsystem.

manual: remove hard-coded IPC register layout

It's out of date and not required in the manual, as it can be read from the source.

manual: Minor fixes, notably last vestige of recycling

SELFOUR-209: Document 28-bit badges

SELFOUR-279: rename Wait -> Recv, add wrappers for seL4_Poll and seL4_Wait for notification objects.

This commit deprecates seL4_ReplyWait, removes seL4_NBwait completely,
and changes the return type of seL4_Wait to void (seL4_Wait should be
used for notification objects, and seL4_Recv should be used where
seL4_Wait was used previously for endpoints).

Add seL4_NBWait: non blocking wait for notifications and endpoints.

manual: notification/signalling terminology

Terminology clarification:
- synchronous endpoints -> endpoints
- asynchronous endpoints -> notifications (and notification objects)
- notify -> signal

Also minor language edits.

fix typo in manual

Introduce 'Notification Binding': a new feature which allows a tcb to be bound to a single asynchronous endpoint.

Revert "s/AEP/Notification/ completed commit :-("

Committed to wrong branch

This reverts commit 50810ac44a4f90f07cfe1aba6f8bf14c30f1d85d.

s/AEP/Notification/ completed commit :-(

Had forgotten the "-a", bear with me, I'm a git newbie...

Release snapshot