DOC: How to install with conan. Downgraded cmake requirements.

CMakeLists.txt

@@ -18,7 +18,7 @@
 # along with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 
-cmake_minimum_required(VERSION 3.14)
+cmake_minimum_required(VERSION 3.13)
 
 set(libcaosdb_VERSION 0.0.5)
 set(libcaosdb_COMPATIBLE_SERVER_VERSION_MAJOR 0)

README_SETUP.md

 # How to Develop and Use Libcaosdb
 
-## Build
+## Requirements ##
+
+- conan: `pip install conan`
+- cmake >= 3.13
+- (Only necessary when building from the git sources) `git submodule update --init proto`
+
+## Semi-manual build
 
 We use [cmake](https://cmake.org) as build tool.
 
-1. `mkdir build && cd build/`
+1. `mkdir build && cd build`
 2. `conan install .. -s "compiler.libcxx=libstdc++11"`
 3. `cmake -B . ..`
 4. `cmake --build .`
@@ -29,6 +35,13 @@ have to add `build/lib/` (or, alternatively after installation,
 `CMAKE_INSTALL_PREFIX/lib`) to your `DYLD_LIBRARY_PATH` environmental
 variable.
 
+## Building with Conan ##
+
+Building and installing libcaosdb with Conan is just a single command:  
+`conan create . -s "compiler.libcxx=libstdc++11"`
+
+For MacOS, you probably should adjust the option as mentioned above.
+
 ## Unit Tests
 
 ### Build