re-structure cfg-buildslaves manual page

* put documentation for supported latent buildslaves into separate
  documents
* polish a bit each page to give an overview of what they provide

Fixes ticket:2861
Merge sa2ajj/buildbot:bugfix-2861 (PR #1232)
Remove the "lone pipe" exception in ShellCommand argument handling

As discussed in
<http://news.gmane.org/find-root.php?group=gmane.comp.python.buildbot.devel&article=10518>.
This makes it possible to pass a pipe as an argument, plus it makes argument
handling consistent between Windows and Unix-likes.
Stop using BuildStepStatus when running steps
Update status string handling for most tests

There are still some failing tests due to a lingering issue around
BuildStep no longer supporting a `describe` method.
add more compatibility for old-style steps

* BuildStep implements describe()
* Factor out command_to_string
Fix ShellSequence status strings; do error reporting in twistd.log
fix remaining tests
Remove the BuildSetStatus class, still allowing unpickling
remove LogFile and HTMLLogFile to buildbot.util.pickle
add tests for get{Current,Result}Summary
test for and consume warnings about legacy GSP
correctly set the path module for p4 tests on windows

This fixes #2916.
Merge pull request #1237 from djmitche/bug2916

correctly set the path module for p4 tests on windows
Merge pull request #1235 from djmitche/gsp-warnings

test for and consume warnings about legacy GSP
Fix the logviewer
misc fixes to the UI

- fix breadcrumbs
- add breadcrumbs on more pages
- make logviewer full screen
- automaticly create slugs for logs
- fix log url (name vs slugs)
- display durations in build summaries
- fix rotation animation on chevrons
- fix mq event matchers (it matched too much events, resulting in weird update in UI)

Signed-off-by: Pierre Tardy <pierre.tardy@intel.com>
Enhance debugging of custom steps
logviewer: fix 2 issues

- autoscroll did not work with wrapped line: dont wrap lines, and use scroll
- log viewer did not display one-liners

Signed-off-by: Pierre Tardy <pierre.tardy@intel.com>
build page: enhance the previous build next build links

Those links are now utf-8 arrows, only displayed when they make sense