Dear ImGui Implementation (#598)

* added imgui as dependency

* imgui renderer/basic input implementation

* imgui: add layers system

Add video info layer to show fps. Press F10 to toggle it.

* imgui: add custom imgui config

* imgui: gamepad capture, stopping propagation

* imgui: changed config & log file path to use portable dir

* videoout: render blank frame when video output is closed

required to render imgui even when game has no video output

- fixed merge compile-error

src/common/assert.cpp

@@ -18,3 +18,8 @@ void assert_fail_impl() {
     Crash();
     throw std::runtime_error("Unreachable code");
 }
+
+void assert_fail_debug_msg(const char* msg) {
+    LOG_CRITICAL(Debug, "Assertion Failed!\n{}", msg);
+    assert_fail_impl();
+}