Adding required DISCLAIMER file (apache#1765)

INCUBATOR projects are required to have a DISCLAIMER file for their
releases.

Signed-off-by: Jason Porter <[email protected]>

DISCLAIMER

@@ -0,0 +1,23 @@
+Apache KIE (incubating) is an effort undergoing incubation at The Apache Software
+Foundation (ASF), sponsored by the name of Apache Incubator. Incubation is
+required of all newly accepted projects until a further review indicates that
+the infrastructure, communications, and decision making process have stabilized
+in a manner consistent with other successful ASF projects. While incubation
+status is not necessarily a reflection of the completeness or stability of the
+code, it does indicate that the project has yet to be fully endorsed by the ASF.
+
+Some of the incubating project’s releases may not be fully compliant with ASF
+policy. For example, releases may have incomplete or un-reviewed licensing
+conditions. What follows is a list of known issues the project is currently
+aware of (note that this list, by definition, is likely to be incomplete):
+
+* Hibernate, an LGPL project, is being used. Hibernate is in the process of 
+  relicensing to ASL v2
+* Some files, particularly test files, and those not supporting comments, may
+  be missing the ASF Licensing Header
+
+If you are planning to incorporate this work into your product/project, please
+be aware that you will need to conduct a thorough licensing review to determine
+the overall implications of including this work. For the current status of this
+project through the Apache Incubator visit:
+https://incubator.apache.org/projects/kie.html