* siri/doc-upgrade/OTP-11717:
  Add documentation about upgrade
  Add info about upgrade of core applications

The example of how to create a first target system, which is located
in the System Principles document, is now extended to also include an
example of code upgrade.

A new chapter is added to System Principles explaining different
issues when upgrade includes new versions applications within
Erlang/OTP.

* mange/update_source_build_doc/OTP-10269:
  Add link to app resource file reference
  Correct and clean up documentation
  Delete obsolete verification doc
  Remove installation instruction for unix binary and reorder chapters

The build and install documentation was not complete
and needed some restructuring.

Non-Windows binaries are not released any longer. Instructions are hence removed.

* egil/maps-doc:
  doc: Add Maps example for sequential programming
  doc: Mention map expressions and map guards
  doc: Add maps to reference manual
  edoc: Add map/0 as a new predefined type
  doc: Descripe Maps type syntax
  doc: Clearify language of user-defined attributes
  doc: Document Maps datatype in reference manual
  erts: Document map guard functions
  erts: Fix is_map/1 spec