add 'chars' parameter to password plugin to allow custom character set

It accepts comma separated list of names that are
either string module attributes (ascii_letters,digits, etc)
or are used literally

To enter comma use two commas ',,' somewhere - preferably at the end
Qoutes and double qoutes are not supported
filter out qoutes since they cause random errors
Merge pull request #4078 from mkaluza/ansible

add 'chars' parameter to password plugin to allow custom character set