Switches to Findbugs @Nullable and @Nonnull instead of jetbrains. This removes an external JAR dependency and should make it easier for us to submit artifacts to maven central.
Merge branch '2.1M2' into qa

Conflicts:
	threadfix-cli-importers/src/main/java/com/denimgroup/threadfix/importer/cli/ScanParser.java
	threadfix-main/pom.xml