[SYNCOPE-529] provided proxy feature to installer

git-svn-id: https://svn.apache.org/repos/asf/syncope/branches/1_2_X@1627813 13f79535-47bb-0310-9956-ffa450edef68
[SYNCOPE-529] merge from branch 1_2_X

git-svn-id: https://svn.apache.org/repos/asf/syncope/trunk@1627815 13f79535-47bb-0310-9956-ffa450edef68