Porting advanced embargo function to JSPUI

Fixed some codes as the code reviews by helix84

reverted the api of BrowseItem to its original

revert build.properties

Porting advanced embargo function to JSPUI, revised version
correct some strings and comments
DS-1622 Porting of the Login As feature to JSPUI
Turn xmlui/jspui.user.assumelogin property to the new webui.user.assumelogin, add custom jsp error to show no loginas action reason
Add link to return at epeople admin page, Add throw only authorizeexception, Show custom errorpage in the case of superadmin loginas superadmin
Add one error jsp with only a message, remove i18n for authorize exception message
Merge pull request #1 from lap82/DS-1622

[DS-1622] Uniform property xmlui/jspui in webui.user.assumelogin
Cleanup: this jsp is not an errorPage
Logout from a loginAs user will relogin the previous user
Merge pull request #286 from abollini/DS-1622

DS-1622 Porting of the Login As feature to JSPUI
Merge remote-tracking branch 'helix84/zuki-embargo3-rebased' into DS-1360

Conflicts:
	dspace-api/src/main/resources/Messages.properties
	dspace-jspui/src/main/webapp/styles.css
Renamed xmlui.submission.restrictstep.* configuration parameters to webui.submission.restrictstep.*
Renamed xmlui.submission.restrictstep.* configuration parameters to webui.submission.restrictstep.*
Organize import, wrong header for end date column
Avoid advanced form to repropose the first embargo policy after any confirm & add
added a license header
Merge pull request #298 from abollini/DS-1360

DS-1360 Porting advanced embargo function to JSPUI