Reworked manage provider to use 'username' instead of 'id' for the user's name

The original code ignores the use of the 'username' attribute.

This fix allows the use of 'username' which also bypasses some user name
limitations inherent to data bags.

For example, I wanted to have a user name with a period in it but the
data bag 'id' is limited to alphanumeric, -, _ characters.
[COOK-1583] Ability to set a password

When a 'password' entry exists in the users data bag, chef will set the user's
password.

Depenes on an Omnibus ruby, since it will ship with ruby-shadow. Not attempting
to make this backward compatible with non-omnibus rubies.

The password would not be saved to the data bag in clear text. It would be
hashed, which the user resource already accepts.  Hashing can be achieved with:
    `openssl passwd -1 "plaintextpassword"`
Merge pull request #9 from retr0h/COOK-1583

[COOK-1583] Ability to set a password
release v1.1.4
Merge pull request #6 from jeremiahsnapp/COOK-1398

[COOK-1398] Provider manage.rb ignores username attribute
[COOK-1582] Change ssh_keys to an array

Currently the users cookbook allows a string or an array for the ssh_keys value.
Updated documentation to reflect the recommended usage as an Array.
Merge branch 'COOK-1582'
Adding whyrun support to users/manage.rb
Merge pull request #15 from opscode-cookbooks/whyrun

Adding whyrun support to users/manage.rb
Ignore vim swap files
Allow specifying of ssh private and public keys for a user
add name attribute to metadata
Merge branch 'master' of git://github.com/opscode-cookbooks/users into COOK-1842
Don't assume dsa keys, detect rsa vs. dsa
release v1.2.0
[COOK-2021] Empty default recipe for including users LWRPs
Merge pull request #16 from trobrock/COOK-1842

[COOK 1842] Allow specifying of ssh private and public keys for a user
Merge pull request #19 from bflad/empty_default_recipe

[COOK-2021] Empty default recipe for including users LWRPs
release v1.3.0
[COOK-2479] Permit users cookbook to work with chef-solo if edelight/chef-solo-search is installed.