Use Catch for our test suite

`make check` is also added to compile and run the tests
Catch is fetched with cmake automatically into the build directory when needed

tests/database.cpp

@@ -0,0 +1,30 @@
+#include "catch.hpp"
+
+#include <database/database.hpp>
+
+#include <unistd.h>
+#include <config/config.hpp>
+
+TEST_CASE("Database")
+{
+#ifdef USE_DATABASE
+  // Remove any potential existing db
+  ::unlink("./test.db");
+  Config::set("db_name", "test.db");
+  Database::set_verbose(false);
+  auto o = Database::get_irc_server_options("zouzou@example.com", "irc.example.com");
+  o.update();
+  auto a = Database::get_irc_server_options("zouzou@example.com", "irc.example.com");
+  auto b = Database::get_irc_server_options("moumou@example.com", "irc.example.com");
+
+  // b does not yet exist in the db, the object is created but not yet
+  // inserted
+  CHECK(1 == Database::count<db::IrcServerOptions>());
+
+  b.update();
+  CHECK(2 == Database::count<db::IrcServerOptions>());
+
+  CHECK(b.pass == "");
+  CHECK(b.pass.value() == "");
+#endif
+}