Added support for not saving options, get by name.

Motivation: I don't want to save all my options. I would rather just
get options by name. There for I added some methods:

    <T> T getValue(String long_form)
    <T> T getValue(String long_form, T default)
    <T> Collection<T> getValues(String long_form)

They work the same way as getOptionValue(Option<T> o) etc...

A sanity test is written but more testing should probably be done.