state in class javadoc that null keys and values are not allowed; add javadoc to all methods that take keys or values as params and do not allow null stating an NPE is thrown for null keys or values
add missing null key/value checks to putAll() impl; remove un-needed null value check from 2-param putAsync() (4-param putAsync() will handle the check)
add a testNullChecks() test method that verifies that all IMap methods that take keys or values as params and do not allow null, throw a NullPointerException if passed a null key or value
remove undesired formatting added by IntelliJ
remove undesired formatting added by IntelliJ (take 2...)
remove NPE on null key assertions for IMap#addEntryListener() methods
Merge pull request #1117 from ispringer/feature-imap-null-values-master

improve code, javadoc, and tests relating to disallowed null keys/values