webadmin: Store subtab height in browser

- This patch adds the ability to store the subtab height in
  the browser local storage. In both user portal and webadmin

Change-Id: I2a7cb529914703e71da9ac323ee15bdb68b1449a
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1140249
Signed-off-by: Alexander Wels <awels@redhat.com>