Merge pull request #506 from volaya/diff_exception

Fixed NPE when printing an attribute diff with null value
Merge pull request #503 from volaya/reset_conflict

Fixed resetOp, when used during conflict
Merge pull request #500 from volaya/show_improvements

Improved show command
Merge pull request #497 from volaya/tags

Added RevTag to text serialization factory
Merge pull request #501 from volaya/merge-abort

fixed merge operation. It required commit when aborting.
Merge pull request #512 from volaya/blame_conflict

Allow the blame operation to run during conflicts
Merge pull request #504 from volaya/exit_code

Fixed exit codes. It was swallowing them and not returning them correctly
Merge pull request #498 from volaya/format-patch

fixed issue in format-patch command
Merge pull request #508 from volaya/rebase_equal_changes

Fixed issue with false conflicts being signaled when both branches had made exactly the same change
Improvements in OSM mappings

Support for adding default fields in MappingRule.java
Better handling of lies/plygons and extra options

This commit addresses #513 and #514

Documentation has been updated and the OSM chapter cleaned, removing a section that shouldn't be in the manual
fixed issues with default field names
fixed issue when unmapping polygons

fixes #522
fixed unmaping issues.

-avoid creating null values when unmapping
-handle default fields correctly