Add ability to exclude file names from VFS sync

This patch is for mitigating the inability of the OpenCms VFS sync to
exclude VCS metadata. The opencms-workplace.xml now supports two
additional tags:
<workplace>
  [...]
  <synchronization>
    <exclude-pattern>^.</exclude-pattern>
    <exclude-pattern>^CVS$</exclude-pattern>
    [...]
  </synchronization>
</workplace>
The patterns are parsed as Java RegExes and will neither be imported to
the VFS nor deleted from the RFS by the synchronization process.

This Patch is missing unit tests and only contains the english and
german localization.
Fix key in german messages file
Exception handling of invalid regex on init
Exchanged special characters with their unicode representation to avoid
encoding issues.
Updated class path.
Improved file reading to be more robust when test cases are executed
through ant.
Added check style target to build.xml.
Ensuring the existence of the parent directory.
Fixing issue with message bundle test when properties files where not
created within the test class path.
Fixing null pointer issue due to optional solr configuration.
Changed handling of absolute internal links.
Changed test cases to reflect changed handling when recreating a
resource with the same name.
Removing redundant modifier.
Simplified boolean return check.
Only use the Solr configuration for those test cases that really need
it.
Fixing stack overflow issue.
Renaming user agent class.
Extended check style target.
Preventing nested element groups.
Removing unmappable character for encoding ASCII.