Fixes includes wrt opm-parser PR-656

Several files stopped compiling due to relying on opm-parser headers
doing includes. From opm-parser PR-656
https://github.com/OPM/opm-parser/pull/656 this assumption is no longer
valid.

tests/test_timer.cpp

@@ -27,6 +27,7 @@
 
 #define BOOST_TEST_MODULE OPM-TimerTest
 #include <boost/test/unit_test.hpp>
+#include <boost/date_time/posix_time/posix_time.hpp>
 
 #include <opm/parser/eclipse/Parser/Parser.hpp>
 #include <opm/parser/eclipse/Parser/ParseMode.hpp>