Improve the HTTP plugin by allowing configuring a proxy and friendly name per URL.

Note that the configuration file syntax has changed. You need one "url"
variable per URL now, numbered starting with 1, e.g. url1, url2, url3.
Each one can be configured by suffixing its variable, e.g. url1_proxy,
url2_proxy, etc.
Add our "all processes" monitoring plugin, cleaned up, and a page fault plugin.
These plugins should be executable.
Fix process labels.
Fix string comparison.
Add a plugin for adding up any number column output by ps.
Improve the left-side label of the graph.
Merge pull request #206 from aptivate/master

Improved HTTP plugin, new CPU and page fault plugins