Replace beanshell standard help system with a more extensible help system

[stefanofornari]

I'd like to be able to provide a flexible and simple help system for 3rd party commands or added commands. This is how it should work:

bsh.help shall point to a directory where the help text of the various commands will be stored, one file per command. The help file shall be named [command name].txt and follow the resource conversion of turning package namespaces into subfolders (e.g. help file com/acme/app/show.txt is for command com.acme.app.show).

A new command help() shall be provided. This lists all help files and print them all on the console's output stream. If help() is used with one or more string arguments, the help files of the given commands shall be printed.

bsh.help shall default to /help

This should replace the use of bsh.help. which quite limited in the length and formatting of the text.

[stefanofornari]

Implemented in v1.3.0