add print_text_table, print_entry to CLIHandler

add print_text_table, print_entry to CLIHandler

These two function could serve as a generic output sub for various CLI
utilities
 * print_text_table prints an array of objects in a tabular fashion,
   the formating is passed as an array containg hashes with titles, maximal
   lengths and default values. This way we can stay extensible, by adding other
   keys to the formatting options
 * print_entry prints out a single entry, handling array-refs as properties

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>