Revised the write_hdf5_xml tool considerably.
- The extent section needed some revamping.
- Added baseline method and orbit type to InSAR metata.
- Renamed files_t into params_t and related variable accordingly.
- Extracted remaining time stamps for processing steps.
- Added the DEM URL and troposphere to the parameter list.
Merge pull request #210 from rudigens/roipac

Revised the write_hdf5_xml tool considerably.