[FIX JENKINS-23041] Fix systemInfo for offline slaves

- Don't show link in sidebar
- Make systemInfo page more robust when accessed via URL
[FIX JENKINS-18048] Fix link of SCMTriggerCause from UpstreamCause

- UpstreamCause now tries to initialize upstream causes with the
  correct build in onLoad
- SCMTriggerCause stores build reference and uses its URL to build
  absolute link to changelog
[FIX JENKINS-14538] Improve builds dir input validation
[JENKINS-14583] Move replacement into shared function for reuse
[FIXED SECURITY-133] Restrict access to SCMTrigger status page

The page shows the names and URLs of all jobs currently busy with
polling. This includes jobs users might not regularly be able to
access and might therefore reveal otherwise hidden information.
[FIXED JENKINS-18902] Exclude lower bound of range from changes
Merge branch 'master' into JENKINS-18048

Conflicts:
	core/src/main/java/hudson/triggers/SCMTrigger.java
[FIX JENKINS-22971] Show full project name when in folder.
[JENKINS-14583] Fix tests
[FIXED JENKINS-23636] Indicate node the job workspace is on
[FIXED JENKINS-23893] Top level ListView is not updated when job is renamed/deleted
add missing td elements for table rows without help
Merge pull request #1323 from olivergondza/JENKINS-23893

[FIXED JENKINS-23893] Top level ListView is not updated when job is renamed/deleted
resolves issue JENKINS-23956 - wrong portuguese translation for Util.day
Merge pull request #1333 from froque/JENKINS-23956

resolves issue JENKINS-23956 - wrong portuguese translation for Util.day
UI - Prevent executor# col expanding

As page expands, the executor number column within the Build Executor Status table expands. By giving a definitive width, column will remain fixed when the page expands. If the executor# is > 99, the column can still expand due to   middle column remaining a flexible width.
Merge pull request #1335 from lrobertson39/master

UI Improvement - Prevent executor# col expanding
Shrinks the header bar from 50px to 40px.
updates to the login/sign up links

- remove the underline to make them a little less heavy
- add hover states - underline + color change.
- remove inline style from login link - is this a security risk, somehow?
new jelly tag <f:helpLink> for displaying help links

The new tag ensures that whenever there is no help available, a blank
table cell is output.