Linode account utility, exception catching

This commit introduces support for listing account-level information.

This commit also includes additional error-catching for some rare
cases where output would fail due to an uncaught exception.
Account info should 'show', fix spurious comments

Account info should present itself in 'show' format, rather than
'list' format, especially since only one account is dealt with at
a time.

This commit also uncomments a block of code that shouldn't have
been commented.
provides help specific to the command/action
fix for displaying help without an action
Use display group in 'list', make tables pretty

This is a minor overhaul of the Linode 'list' action. Linodes are
now grouped by their display group (if one exists). Additionally,
the list output is slightly more stylized.
Improved plan/plainid handling.

Plans can now be specified easily, linode1024, linode2048, ...
- Allows for "Linode 1024" style too.
Documentation updates for developer release #4
String formatting in account info, general tidying
General housekeeping and doc updates
Fix documentation typo