Update workspace command to support deleting all workspaces

[jhart-r7]

I use workspaces to separate the various things I happen to be working on, but it is pretty rare that I need to keep any workspace for very long. After a while I get a lot and have the urge to purge and prefer to not have to do this at the database level, so I figured the ability to delete all workspaces would be helpful. This complements other delete functionality but is a bit more dangerous.

Validation

• Specs pass
• Basic CLI testing:

msf > workspace 
* default
msf > workspace -a foo bar baf blargh
[*] Added workspace: foo
[*] Added workspace: bar
[*] Added workspace: baf
[*] Added workspace: blargh
msf > workspace -d blargh 
[*] Deleted workspace: blargh
[*] Switched workspace: default
msf > workspace 
* default
  foo
  bar
  baf
msf > workspace -D
[*] Deleted and recreated the default workspace
[*] Deleted workspace: foo
[*] Deleted workspace: bar
[*] Deleted workspace: baf
msf > workspace 
* default

Also, I know the specs I added are currently broken, because the existing testing framework only tests stuff that comes from print_line and print_error. I could convert workspace to use print_line or I could update

[wvu]

I implemented this previously as workspace -d (without any options) and then tossed the code because it was deemed dangerous. Totally forgot about the convention of using an uppercase short option to denote "everything." Much better!

[wvu]

Love it! Thanks again, @jhart-r7.