Enhancements proposal for gdal_merge.py

[pedera]

1. Made gdal_merge into a module: it can be imported and executed directly from python code. It can still be used as a command line, of course.

2. Added an option -progress that will present unobtrusive feedback on the progress. It counts down the number of files left to merge.

3. Added a global version variable, now that gdal_merge also is a library. The value should be set by the versioning system using '$id$'[5:-1], maybe this should be done differently?

[warmerdam]

Chaitanya,

Could you review, and if appropriate incorporate the provided changes in trunk? I do not believe they are appropriate for 1.6 branch.

[chaitanya]

Applied the patch in trunk (r18412)