Switch from autotools to CMake build system (#23)

* Switch from autotools to CMake

* CMake: require at least cmake 3.8

* cmake: updates for tests

src/Makefile.am

@@ -1,27 +0,0 @@
-
-lib_LTLIBRARIES = libsdbus-c++.la
-
-libsdbus_c___la_SOURCES = \
-	Connection.cpp \
-	ConvenienceClasses.cpp \
-	Message.cpp \
-	MethodResult.cpp \
-	Object.cpp \
-	ObjectProxy.cpp \
-	Types.cpp \
-	Error.cpp \
-	VTableUtils.c
-
-libsdbus_c___la_LIBADD = @SYSTEMD_LIBS@
-
-# Setting per-file flags
-AM_CPPFLAGS = -I$(top_srcdir)/include
-AM_CXXFLAGS = @libsdbus_cpp_CFLAGS@ @SYSTEMD_CFLAGS@ -std=c++17 -pipe -pedantic -W -Wall
-AM_LDFLAGS = @libsdbus_cpp_LIBS@ @SYSTEMD_LIBS@ 
-
-libsdbus_c___la_LDFLAGS = -version-info 0:0:0
-
-# Cleaning
-CLEANFILES = *~ *.lo *.la
-MOSTLYCLEANFILES = *.o
-DISTCLEANFILES = Makefile Makefile.in