find: Rational expression.

* src/dctc/java/com/dataiku/dctc/command/Find.java: Make available the
  rational expression.
Delete misplaced comments.

* src/dctc/java/com/dataiku/dctc/file/LocalFile.java: Here.
Add missing test for globbing.

* src/dctc/test/com/dataiku/dctc/test/GlobbingTest.java: Here.
Delete useless comment.

* src/dctc/java/com/dataiku/dctc/file/SshFileBuilder.java: Introduce
  without any changes in the files. Revert this comment.
ssh: Get the username from the ssh configuration file

Closes #67.

* src/dctc/java/com/dataiku/dctc/file/SshFileBuilder.java: Here.
* src/dctc/java/com/dataiku/dctc/file/SshFileBuilder.java (checkAllowedOnly):
  The user name could be configured with the ssh configuration
  file. Is no more mandatory.
ssh config: Make non case sensitive host/username/key name...

* src/dctc/java/com/dataiku/dctc/configuration/SshConfig.java: Compute
  toLowerCase for each string.