add reportreserved parameter for df plugin
Merge pull request #139 from mmoll/reportreserved

add reportreserved parameter for df plugin
unixsock plugin: Implement the "DeleteSocket" option.
Merge pull request #140 from txaj/unixsock-delete-opt

Unixsock delete option
Create collectd::plugin::curl class and collectd::plugin::curl::page defined type
Post and Headers were introducted in collectd >= 5.3
Dealing with the uniqueness of instancied resources versus the non uniqueness of the plugin instance in <Page>