Added amend option to commit operation
Fixed an issue which caused points from OSM to not be downloaded.

Nodes that were not part of ways were not being downloaded.
Make GeogitFeatureStore.getTransaction synchronized.

GeogitFeatureStore.setTransaction method was synchronized but the
getTransaction method was not. This may result in incorrect behavior
at runtime, as callers of the get method will not necessarily see
a consistent state for the object.
Fix exception created and dropped rather than thrown
Fix possible NPE reference or incompatible types equality check.

UpdateRefWeb was calling equals against newRef (String) and ObjectId.NULL (ObjectId)
and didn't check newRef for nullity.
Merge pull request #388 from jdgarrett/osm-download-fix

Fixed an issue which caused points from OSM to not be downloaded.
Merge branch 'amend' of git://github.com/volaya/GeoGit into volaya-amend

Conflicts resolved:
	src/cli/src/main/java/org/geogit/cli/porcelain/Commit.java
	src/core/src/main/java/org/geogit/api/porcelain/CommitOp.java
	src/core/src/test/java/org/geogit/test/integration/CommitOpTest.java
Merge branch 'volaya-amend'