Fix sphinx-build 'unbalanced parenthesis' error.

[sebastic]

As reported in Debian Bug #811262, tilecache failed to build with sphinx 1.3.4:

  sphinx-build docs/ docs/html/
  Running Sphinx v1.3.4
  making output directory...
  loading pickled environment... not yet created
  building [mo]: targets for 0 po files that are out of date
  building [html]: targets for 9 source files that are out of date
  updating environment: 9 added, 0 changed, 0 removed
  reading sources... [ 11%] CONTRIBUTORS
  reading sources... [ 22%] Caches
  reading sources... [ 33%] EXAMPLES
  reading sources... [ 44%] Example.py

  Exception occurred:
    File "/usr/lib/python2.7/re.py", line 251, in _compile
      raise error, v # invalid expression
  error: unbalanced parenthesis

Fixed by using single lines for the properties.