Allow to have "=" in value of custom fields for OClass, OProperty and ODatabaseRaw.

This is PR for Issue #2804.

ATTENTION: Currently, tests are failing. But if I'm correct: that's not because of my fix.
Please see below:

```
testTransactionalGraphTestSuite on testTransactionalGraphTestSuite(com.tinkerpop.blueprints.impls.orient.OrientGraphClassicRemoteTest)(com.tinkerpop.b
lueprints.impls.orient.OrientGraphClassicRemoteTest)  Time elapsed: 0.036 sec  <<< FAILURE!
org.junit.internal.AssumptionViolatedException: got: <DEV>, expected: <RELEASE>
        at org.junit.Assume.assumeThat(Assume.java:95)
        at com.tinkerpop.blueprints.impls.orient.OrientGraphClassicRemoteTest.setUp(OrientGraphClassicRemoteTest.java:18)

testGraphMLReaderTestSuite on testGraphMLReaderTestSuite(com.tinkerpop.blueprints.impls.orient.OrientGraphClassicRemoteTest)(com.tinkerpop.blueprints.
impls.orient.OrientGraphClassicRemoteTest)  Time elapsed: 0 sec  <<< FAILURE!
org.junit.internal.AssumptionViolatedException: got: <DEV>, expected: <RELEASE>
        at org.junit.Assume.assumeThat(Assume.java:95)
        at com.tinkerpop.blueprints.impls.orient.OrientGraphClassicRemoteTest.setUp(OrientGraphClassicRemoteTest.java:18)

testVertexTestSuite on testVertexTestSuite(com.tinkerpop.blueprints.impls.orient.OrientGraphClassicRemoteTest)(com.tinkerpop.blueprints.impls.orient.O
rientGraphClassicRemoteTest)  Time elapsed: 0 sec  <<< FAILURE!
org.junit.internal.AssumptionViolatedException: got: <DEV>, expected: <RELEASE>
        at org.junit.Assume.assumeThat(Assume.java:95)
        at com.tinkerpop.blueprints.impls.orient.OrientGraphClassicRemoteTest.setUp(OrientGraphClassicRemoteTest.java:18)

testGraphSONReaderTestSuite on testGraphSONReaderTestSuite(com.tinkerpop.blueprints.impls.orient.OrientGraphClassicRemoteTest)(com.tinkerpop.blueprint
s.impls.orient.OrientGraphClassicRemoteTest)  Time elapsed: 0 sec  <<< FAILURE!
org.junit.internal.AssumptionViolatedException: got: <DEV>, expected: <RELEASE>
        at org.junit.Assume.assumeThat(Assume.java:95)
        at com.tinkerpop.blueprints.impls.orient.OrientGraphClassicRemoteTest.setUp(OrientGraphClassicRemoteTest.java:18)

testGMLReaderTestSuite on testGMLReaderTestSuite(com.tinkerpop.blueprints.impls.orient.OrientGraphClassicRemoteTest)(com.tinkerpop.blueprints.impls.or
ient.OrientGraphClassicRemoteTest)  Time elapsed: 0 sec  <<< FAILURE!
org.junit.internal.AssumptionViolatedException: got: <DEV>, expected: <RELEASE>
        at org.junit.Assume.assumeThat(Assume.java:95)
        at com.tinkerpop.blueprints.impls.orient.OrientGraphClassicRemoteTest.setUp(OrientGraphClassicRemoteTest.java:18)
```
And lots of stuff like that.