This patch allows the configuration values to be overridden from the
command-line, with a new -config_overrides flag.
There is a fairly specific use case for this, when editing the
configuration file is not feasible or convenient (e.g. running an
user-supplied configuration in a managed environment).
This patch adds man pages for chasquid's main commands and
configuration. They are generated using pod2man (commonly used for this,
and included with perl in most distributions).
The generated man pages are included to avoid introducing a dependency
for such simple task, similar to how we handle protocol buffer generated
files.
