Optional: Move optional-lite to the include/third-party directory

This fixes the use case of adding the include folder
manually to an outside project.

include/icsneo/third-party/optional-lite/conanfile.py

@@ -0,0 +1,27 @@
+from conans import ConanFile, CMake
+
+class OptionalLiteConan(ConanFile):
+    version = "3.4.0"
+    name = "optional-lite"
+    description = "A single-file header-only version of a C++17-like optional, a nullable object for C++98, C++11 and later"
+    license = "Boost Software License - Version 1.0. http://www.boost.org/LICENSE_1_0.txt"
+    url = "https://github.com/martinmoene/optional-lite.git"
+    exports_sources = "include/nonstd/*", "CMakeLists.txt", "cmake/*", "LICENSE.txt"
+    settings = "compiler", "build_type", "arch"
+    build_policy = "missing"
+    author = "Martin Moene"
+
+    def build(self):
+        """Avoid warning on build step"""
+        pass
+
+    def package(self):
+        """Run CMake install"""
+        cmake = CMake(self)
+        cmake.definitions["OPTIONAL_LITE_OPT_BUILD_TESTS"] = "OFF"
+        cmake.definitions["OPTIONAL_LITE_OPT_BUILD_EXAMPLES"] = "OFF"
+        cmake.configure()
+        cmake.install()
+
+    def package_info(self):
+        self.info.header_only()