ANNIS 3.1.7

This is a bugfix release that addresses the following issues:

#340 fixed bug in CorefVisualizer. The annotation name is now displayed
#336 Existence of directory is not checked when saving corpus properties
#332 document browser needs long time to load when there is a larger number of metadata

We would like to give special thanks to Adriane Boyd and Lari Lampen for providing the bug fixes for the issues #332 and #336.