camel-hdfs - Add maxMessagesPerPoll for Consumer

Add a maxMessagesPerPoll property, like the file component has.

* To define a maximum messages to gather per poll.
* By default no maximum is set. Can be used to set a limit of e.g. 1000 to avoid when starting up the server that there are thousands of files.
* Set a value of 0 or negative to disabled it.
* Notice: If this option is in use then the File and FTP components will limit before any sorting.
* For example if you have 100000 files and use maxMessagesPerPoll=500, then only the first 500 files will be picked up, and then sorted.