Minor fixes and changes to cli plumbing commands (blame and diff-tree)

Minor edit to documentation
added raw version to show command
Made diff-tree use plumbing DiffTree operation instead of DiffOp

Adapted functional tests for diff-tree
Fixed issues in show command
Merge branch 'plumbing' of github.com:volaya/GeoGit into volaya-plumbing
Restore the use of checkParameter and newAnsi in Show.java
fixed issue in Blame operation
fixed unflushed error message in console, from Diff-tree command
Merge pull request #321 from volaya/plumbing

Minor fixes and changes to cli plumbing commands (blame and diff-tree)