Set version to 1.3.1 an did multiple Bug fixes:
 - Allow user edit of Target TeamMentor instance: (https://github.com/TeamMentor/TeamMentor_Eclipse_Plugin/issues/17)
 - Use TeamMentor Icons and not Eclipse default ones (https://github.com/TeamMentor/TeamMentor_Eclipse_Plugin/issues/18)
 - Change top menus (https://github.com/TeamMentor/TeamMentor_Eclipse_Plugin/issues/13 and https://github.com/TeamMentor/TeamMentor_Eclipse_Plugin/issues/12)
 - Show TM articles in same window (https://github.com/TeamMentor/TeamMentor_Eclipse_Plugin/issues/1)
 - Added properties page
Merge branch '1.3_Issues'