Expose timestamp-age-limit as a property in guacamole.properties.
Merge stephenryoungster-master into stephenryoungster-master

Conflicts:
	src/main/java/com/stephensugden/guacamole/net/hmac/HmacAuthenticationProvider.java
	src/test/java/com/stephensugden/guacamole/net/hmac/HmacAuthenticationProviderTest.java