Add printing of (better) help/usage to console

[grtjn]

if you run Corb2 via Roxy (with latest PR), but don't provide any arguments, you get:

$ ./ml local corb
Jul 15, 2016 9:17:50 AM com.marklogic.developer.corb.Manager main
SEVERE: Error initializing CORB
java.lang.NullPointerException: PROCESS-TASK or PROCESS-MODULE must be specified
    at com.marklogic.developer.corb.Manager.initOptions(Manager.java:336)
    at com.marklogic.developer.corb.Manager.init(Manager.java:204)
    at com.marklogic.developer.corb.AbstractManager.init(AbstractManager.java:173)
    at com.marklogic.developer.corb.Manager.main(Manager.java:162)

Particularly showing java.lang.NullPointerException looks odd. Maybe take MLCP as example?

$ ./ml local mlcp

usage: mlcp COMMAND [ARGS]

Available commands:
  IMPORT  import data to a MarkLogic database
  EXPORT  export data from a MarkLogic database
  COPY    copy data from one MarkLogic database to another
  EXTRACT extract data from MarkLogic forests
  HELP    list available commands
  VERSION print the version

$ ./ml local mlcp import

16/07/15 09:23:29 ERROR contentpump.ContentPump: Error parsing command arguments: 
16/07/15 09:23:29 ERROR contentpump.ContentPump: Missing required option: input_file_path
usage: IMPORT [-aggregate_record_element <QName>]
       [-aggregate_record_namespace <namespace>] [-aggregate_uri_id
       <QName>] [-archive_metadata_optional <true,false>] [-batch_size
       <number>] [-collection_filter <String>] [-content_encoding
       <encoding>] [-copy_collections <true,false>] [-copy_permissions
       <true,false>] [-copy_properties <true,false>] [-copy_quality
       <true,false>] [-data_type <data type>] [-database <database>]
       [-delimited_root_name <root name>] [-delimited_uri_id <column
       name>] [-delimiter <delimiter>] [-directory_filter <String>]
       [-document_type <type>] [-fastload <true,false>]
       [-filename_as_collection <true,false>] [-generate_uri <true,
       false>] [-hadoop_conf_dir <directory>] -host <host>
       [-input_compressed <true,false>] [-input_compression_codec <codec>]
       -input_file_path <path> [-input_file_pattern <regex pattern>]
       [-input_file_type <type>] [-max_split_size <number>]
       [-min_split_size <number>] [-mode <mode>] [-namespace <namespace>]
       [-output_cleandir <true,false>] [-output_collections <collections>]
       [-output_directory <directory>] [-output_graph <graph>]
       [-output_language <language>] [-output_override_graph <graph>]
       [-output_partition <partition name>] [-output_permissions
       <permissions>] [-output_quality <quality>] [-output_uri_prefix
       <prefix>] [-output_uri_replace <list>] [-output_uri_suffix
       <suffix>] [-password <password>] [-port <port>]
       [-sequencefile_key_class <class name>] [-sequencefile_value_class
       <class name>] [-sequencefile_value_type <value type>] [-split_input
       <true,false>] [-streaming <true,false>] [-temporal_collection
       <String>] [-thread_count <count>] [-thread_count_per_split <count>]
       [-tolerate_errors <true,false>] [-transaction_size <number>]
       [-transform_function <String>] [-transform_module <String>]
       [-transform_namespace <String>] [-transform_param <String>]
       [-type_filter <String>] [-uri_id <uri name>] [-username <username>]
       [-xml_repair_level <level>]
 -aggregate_record_element <QName>         Element name in which each
                                           document is found
 -aggregate_record_namespace <namespace>   Element namespace in which each
                                           document is found
 -aggregate_uri_id <QName>                 Deprecated. Name of the first
                                           element or attribute within a
                                           record element to be used as
                                           document URI. If omitted, a
                                           sequence id will be generated
                                           to  form the document URI.
 -archive_metadata_optional <true,false>   Whether to allow empty metadata
                                           when importing archive
...