Bugfix: sd:format-string and sd:format-number

The new xpath model broke the arguments
Merge branch 'hotfix_v1.6' into develop

* hotfix_v1.6:
  Bugfix: sd:format-string and sd:format-number
Fix "planets" example
Move hello world example to documentation

Also update the index files
Merge branch 'hotfix_v1.6' into develop

* hotfix_v1.6:
  Move hello world example to documentation
  Fix "planets" example
Bugfix for xpath expressions foo(bar(arg),x)

There was a nasty error with the following type of xpath
expressions:

sd:format-number(sd:format-string(123.456,'%.2f'), '.', ',')

where the first closing paren was ignored.
Merge branch 'hotfix_v1.6' into develop

* hotfix_v1.6:
  Bugfix for xpath expressions foo(bar(arg),x)