Added a ${GemName}.Builders variant to Asset-Only Gems (#1324)

* Creating Builder variant aliases for all Asset Gems

* Added an AssetGem template for creating an Asset Gem

The AssetGem template is meant for non-code Gems

* Updated the engine_template.py commands to use pathlib

Each of the four commands: create-template, create-from-template,
create-project and create-gem have been updated to use pathlib.Path or
any path manipulation

Fix several python errors when instantiating a template with missing
o3de objects.
For example attempting to use the create-project command with the
"DefaultGem" template would result in a python exception instaed of a
error log and a return value 0..

Added a **force** option to the engine_template commands
to force overriding of existing files

* Optimized search through text files when the create-template command is
run when attempting to replace the license text section

* Adding a Minimal Project Template that contains the minimal set of gems
as stated by UX

* Minor changes to the DefaultProject template. Added a license section to the EngineFinder.cmake

* Adding the MinimalProject to the engine.json file

Gems/AtomContent/ReferenceMaterials/CMakeLists.txt

@@ -0,0 +1,15 @@
+#
+# All or portions of this file Copyright (c) Amazon.com, Inc. or its affiliates or
+# its licensors.
+#
+# For complete copyright and license terms please see the LICENSE at the root of this
+# distribution (the "License"). All use of this software is governed by the License,
+# or, if provided, by the license below or the license accompanying this file. Do not
+# remove or modify any license notices. This file is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#
+
+# This will export its "SourcePaths" to the generated "cmake_dependencies.<project>.assetbuilder.setreg"
+if(PAL_TRAIT_BUILD_HOST_TOOLS)
+    ly_create_alias(NAME AtomContent_ReferenceMaterials.Builders NAMESPACE Gem)
+endif()