Either make tests and examples independent or enable examples when building tests

[barracuda156]

Tests do not run if examples are not explicitly enabled in the build. This is somewhat counter-intuitive: perhaps, either make these separate or make examples a part of tests without a separate configure setting. Otherwise running tests with -DPRIMA_ENABLE_TESTING=ON but without -DPRIMA_ENABLE_EXAMPLES=ON leaves all tests broken.

[zaikunzhang]

Tests do not run if examples are not explicitly enabled in the build. This is somewhat counter-intuitive: perhaps, either make these separate or make examples a part of tests without a separate configure setting. Otherwise running tests with -DPRIMA_ENABLE_TESTING=ON but without -DPRIMA_ENABLE_EXAMPLES=ON leaves all tests broken.

@jschueller Could you have a look! Shouldn't DPRIMA_ENABLE_EXAMPLES be set to ON if DPRIMA_ENABLE_TESTING is ON? Or should we merge the two options? Thank you.