Add vcpkg submodule

.gitmodules

 [submodule "proto"]
 	path = proto
 	url = ../caosdb-proto.git
+[submodule "vcpkg"]
+	path = vcpkg
+	url = https://github.com/microsoft/vcpkg

CMakeLists.txt

@@ -20,6 +20,9 @@
 
 cmake_minimum_required(VERSION 3.13)
 
+set(CMAKE_TOOLCHAIN_FILE "${CMAKE_CURRENT_SOURCE_DIR}/vcpkg/scripts/buildsystems/vcpkg.cmake"
+  CACHE STRING "Vcpkg toolchain file")
+
 set(libcaosdb_VERSION 0.3.0)
 set(libcaosdb_COMPATIBLE_SERVER_VERSION_MAJOR 0)
 set(libcaosdb_COMPATIBLE_SERVER_VERSION_MINOR 9)

vcpkg @ 8ae59b5b

+Subproject commit 8ae59b5b1329a51875abc71d528da93d9c3e8972