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/Common/Utils.cmake b/Common/Utils.cmake
new file mode 100644
index 0000000..d93dcee
--- /dev/null
+++ b/Common/Utils.cmake
@@ -0,0 +1,37 @@
+#-------------------------------------------------------------------------------
+# Copyright (c) 2019-2020, Arm Limited and Contributors. All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+#
+#-------------------------------------------------------------------------------
+
+#[===[.rst:
+Misc utilities
+--------------
+#]===]
+
+include_guard(DIRECTORY)
+
+#[===[.rst:
+.. cmake:command:: check_args
+
+  .. code-block:: cmake
+
+    check_args(func_name REQ_ARG1 REQ_ARG2)
+
+  Helper macro for argument checking in functions. First argument *func_name* is
+  the name of the function, other arguments are the names of the required
+  arguments to that function. The macro iterates through the list, and prints
+  and error message if not all arguments are defined.
+
+#]===]
+macro(check_args)
+	set(_argv "${ARGV}")
+	list(SUBLIST _argv 0 1 _func)
+	list(SUBLIST _argv 1 -1 _args)
+	foreach(_arg IN LISTS _args)
+		if (NOT DEFINED _MY_PARAMS_${_arg})
+			message(FATAL_ERROR "${_func}(): mandatory parameter '${_arg}' missing.")
+		endif()
+	endforeach()
+endmacro()