Add first version of CMake framework code

This commit adds the core elements of the framework and documentation:
 - Map utility: store key-value pairs.
 - Group utility: store build configuration options.
 - STGT API: describe the targets.
 - Compiler abstraction functions for GCC.
 - Other helper functions.
 - New CMake system type called "Embedded", using correct output file
   prefixes and extensions.
 - Sphinx based documentation which includes:
    - licensing information
    - version numbering policy
    - documentation on how-to build the documentation

In addition the following utility files are added:
  - .editorconfig
  - .gitignore

Change-Id: If19a171ef066775d3544fba82f1cc70a5fb0e7d7
Signed-off-by: Balint Dobszay <balint.dobszay@arm.com>
Co-authored-by: Gyorgy Szing <gyorgy.szing@arm.com>
Co-authored-by: Bence Szépkúti <bence.szepkuti@arm.com>
diff --git a/doc/maintainers.rst b/doc/maintainers.rst
new file mode 100644
index 0000000..b87f4a0
--- /dev/null
+++ b/doc/maintainers.rst
@@ -0,0 +1,38 @@
+Maintainers
+===========
+
+|TFACMF| is an Arm maintained project. All contributions are ultimately merged
+by the maintainers listed below. Technical ownership of some parts of the
+codebase is delegated to the sub-maintainers listed below. An acknowledgement
+from these sub-maintainers may be required before the maintainers merge
+a contribution.
+
+This file follows the format of the Linux Maintainers file. For details on the
+meaning of tags below please refer to the `Linux Maintainers file`_.
+
+Main maintainers
+----------------
+:M: Dan Handley <dan.handley@arm.com>
+:G: `danh-arm`_
+:M: Bálint Dobszay <balint.dobszay@arm.com>
+:G: `balintdobszay`_
+:M: György Szing <gyorgy.szing@arm.com>
+:G: `gyuri-szing`_
+:L: |TFACMF-MAIL-LIST|
+
+Sub-maintainers
+--------------------
+
+Currently none.
+
+--------------
+
+.. _danh-arm: https://github.com/danh-arm
+.. _gyuri-szing: https://github.com/gyuri-szing
+.. _balintdobszay: https://github.com/balintdobszay
+
+.. _`Linux Maintainers file`: https://github.com/torvalds/linux/blob/master/MAINTAINERS#L80
+
+*Copyright (c) 2020, Arm Limited and Contributors. All rights reserved.*
+
+SPDX-License-Identifier: BSD-3-Clause