addressed issue https://github.com/globaleaks/GlobaLeaks/issues/300
updated tip status page with context info: https://github.com/globaleaks/GlobaLeaks/issues/513
extended fields with preview key for https://github.com/globaleaks/GlobaLeaks/issues/515
updated tip list with preview (handler and test) https://github.com/globaleaks/GlobaLeaks/issues/515
Merge pull request #149 from globaleaks/issue/513

Issue/513
Merge pull request #148 from globaleaks/issue/515

Issue/515
UT aligned to fix to issue 513
moved supported_extensions in GLSetting
Merge branch 'master' into issue/300
Merge pull request #147 from globaleaks/issue/300

addressed issue https://github.com/globaleaks/GlobaLeaks/issues/300
Merge branch 'master' into extend_expire_date
extended Node and Comment with new fields