More conversion support.

The idea of the script is to get one sample document input, multiple
necessary documents output. For example, say we have an artificial
document sample.docx, the script is to:

    1. copy sample.docx to a uniform test repo
    2. convert sample.docx to sample.doc and save to the uniform test repo
    3. export sample.docx to sample.docx.pdf and save to the uniform test repo

With this commit the above rule applies to

    - doc/docx
    - xls/xlsx
    - ppt/pptx