Enhance requireModule to set a variable indicating whether or not the module was installed

[rkeithhill]

Saw this use case come up during @dchristian3188 user group presentation. I think it is a good idea.

[LaurentDardenne]

Is it not related to this ?

[rkeithhill]

Not quite. The idea is to be able to use a Plaster variable created by the <requireModule> directive within another directive's condition (must appear after the requireModule) in the template. Perhaps another conditional message that gets display if the required module was not found. This may be a generalized concept where certain directives that could have different outcomes would get an attribute like <requireModule name="posh-git" resultVariable="PoshGitStatus"/> that you could use later with say ... condition="$PLASTER_RESULT_PoshGitStatus". This is just early thinking and may change significantly (or not). BTW I'm not 100% committed to this yet. Toying with the idea atm.