Split Office Content into Nested Pages

The Office Importer Application has been improved to generate (by default) non-terminal (nested) pages when the "Split document" option is selected, if the target wiki page is also non-terminal. The following strategy was implemented:

• if the target wiki page is terminal then the "child" pages created by the split operation are also terminal
• if the target wiki page is nested (non-terminal) then:
  • the "child" pages are also nested, if the current user is simple
  • advanced users have a checkbox to control whether the "child" pages are terminal or not, but by default they are not

Besides this, we also did a couple of small improvements to the office import form to:

• filter office files based on media type (when browsing the local file system)
• improve existing field labels and hints, adding missing hints
• hide UI elements that are not relevant for the office import operation
• perform the office import asynchronously and redirect the user directly to the imported page after a successful import operation