add Burstedde benchmark

This is a combination of 10 commits made by @bangerth in #155:
Using files by Iris van Zelst (with only minor edits), add whatever is necessary to reproduce the Burstedde benchmark.
Massage the previous patch into a form that fits in the manual. Also externalize the input file to make sure it gets automatically annotated.
Adapt the benchmark files. Minor edits elsewhere.
Make Iris van Zelst's benchmark into a testcase.
Add an entry.
Re-indent.
Fix descriptions of plugins.
Adjust output to that on the tester.
Revisit and clean up these plugins.
Added material model based on rheology in Morency and Doin, 2004
Formalities
Fixed units in one of the parameter declarations and increase cutoff limits on viscosity.
Improve documentation.
Added changelog entry.
manual: update description for checkpointing
remove trailing whitespace
various latex formatting fixes
update parameters.tex and manual.pdf
Merge pull request #159 from tjhei/docu_fixes

update manual
Testsuite: Cleanup run_testsuite.cmake

This commit cleans up run_testsuite.cmake. It now

 - correctly determines and submits the branch name
 - writes a smaller revision.log without redundant information
 - does not set a subproject per branch anymore
Merge pull request #161 from tamiko/cleanup_run_testsuite_script

Testsuite: Cleanup run_testsuite.cmake

It now 
- correctly determines and submits the branch name
- writes a smaller revision.log without redundant information
- does not set a subproject per branch anymore
Minor style fixes.
Merge pull request #163 from bangerth/const-fixes

Minor style fixes.
Fix subversion keywords

Fix up forgotten $Id: ... $ - tags in several files.

This commit is primarily intended to test dev-vcs/hub [1] for pull-requests
on the command line

[1] https://github.com/github/hub
Merge pull request #164 from tamiko/fix_subversion_keywords

Fix subversion keywords
Be more verbose in a warning message.

In order to track down what's happening, knowing which file we were trying to write to turned out to be about as useful as knowing the processor number.
Minor edits to some text.
Merge pull request #172 from bangerth/doc-fixes

Minor edits to some text.