Support start time in Hosts.Jobs

This is mainly in support of Maintenance, but may be useful in other places as well. See Bug #1544.
Fix compilation

An incorrectly used type would prevent our code from compiling.
Maintenance: Use relative time for job start

Absolute time is not important here, we just want to know if an
abnormally low load can be caused by a recently started job.
Bug #1544
Merge branch 'release/20130411' into new-cluster
Minor changes

-prefix version in footer by "version"
-write out number of cookies as a Comment/Debug string
Start implementing Share Tree (Bug #1588)

(Does not yet compile)
-Add Navigation;
-Add skeleton code in Viewer;
-Add Share_Tree to do the work;
-Expand Parser to work with non-XML data;
-Add Spread_Sheet to store tabular data;

The Spread_Sheet package is to take the same role as XMLAda's Document
et al do for XML data.
Continue with Bug #1588

Package Pipe_Streams is not useable since it is tailored to XML and
Unicode. We provide our own package (Plain_Pipe_Streams) now. This is
not (yet?) a hierarchy -- it is only used in one place.
Refactor: To_String_List

Move To_String_List from Pipe_Streams to Utils to prepare for
Plain_Pipe_Streams (which still has a lot of duplicated code).
Refactor: Usage_Number, Usage_Integer

Move large number types (for usage reports) from Jobs to Utils.
Finish main part of Sharetree (Bug #1588)

The feature is now complete except for minor details, i.e. information
can be used (and checked).
Still open:
-Summary
-Right-bound justification
-Colour codes?
-Check units
-Truncate percentage values (always ending in 00).
Fix CSS (Bug #1594)

One } too many, one missing.
Implement Share Tree summary

This is part of Bug #1588. We simply display total CPU, Mem, and IO
values. Job number is always zero (why?), and Usage totals to 100%
anyway.

Maybe add the mixing formula for Usage? But where do we get that?
Add Hosts.Get_Name

Missing getter function added
Fix Bug #1596

Catch exception caused by inconsistent load (e.g. used slots > total
slots). We display an HTML.Error in this case -- this is part of the
maintenance page, after all, and the bugzilla link is not totally
misplaced, either, since there *is* a bug, just not in qview.
Merge branch 'hotfix/bug#1596' into new-cluster
Merge branch 'hotfix/bug#1596' into develop
version bump
Fix job slot comparison (Bug #1603)

Until now, only the slot_number would be compared. This did not
work correctly when slot ranges were involved. We fix this by
comparing the hash values of the slot range lists.
In order to get reasonable runtime behaviour, we create
Ranges.Slot_Range_List as a private subtype that caches the necessary
hash value (cf Resources.Hashed_List).
Add "old" queue state (Bug #1602)

This state occurs when a queue has been removed from a host, but
cannot be done away with because it still has running jobs on that
host.
This happens only rarely, so it slipped by until now.
For now, we do not do anything with the information collected (unlike
disabled or error).
Merge branch 'hotfix/1.0b2' into new-cluster