Allow inspecting the arguments to networked commands
Merge pull request #810 from boundlessgeo/network-command-introspection

Allow inspecting the arguments to networked commands
catch pre-command hook exceptions so post-command hooks get the error notification
Allow inspecting the arguments to commands working with remotes
Let RemoteException have a non null exception message
Make AbstractRemoteRepo.checkPush() easier to read
skeleton implementations of send/receivepack
Add a post order diff walk and use it for faster fetch/push in LocalRemoteRepo.
Add progress listener to fetch and push
Make transactions copy all refs.

- Move the transactions namespace to refs/transactions
- Make TransactionRefDatabase copy all refs, including remotes, but
 not other transactions` refs.
- Change the semantics of RefDatabase.getAll() to actually return all
refs instead of just the ones under /refs (i.e. also the top level ones
like HEAD, WORK_HEAD, STAGE_HEAD), but not the ones under the transactions
namespace.
Use java.net.URL to parse URLs in org.locationtech.geogig.api.Remote
initial implementation of SendPack
initial implementation of SendPack
osm web api endpoints
Add unit test and some checks for transaction updating remotes refs
Add /osm/download web-api end point. Make it cancelable and run inside a transaction.
make WorkingTree.insert cancelable through ProgressListener
Make async tasks use the transactionId parameter as the rest of the web-api commands
Add docs for OSM web API in the user manual.
More https correctness