Fix argv/exebin, autoconfig, doc theme, updates from the field

* remove newlines from log messages
* add inotify and signalfd apis to glibc ctypes wrapper
* if binary executable is not specified but argument vector is specified, then
  use first element of argument vector as binary executable
* if binary executable starts with forward slash, don't use use exec version
  that does path lookup
* update dump_constants helper to output in python, json, or human format
* automatically load config file from the root of the target filesystem
* update documentation theme to something based on rtd

fix for /proc mounts and `setgroups`

* Intercept requests for /proc mount and use the MS_REC flag on those
* "allow" `setgroups` as it is now used by apt-get

Add argparse remainder and mount failure info

* Add argparse remainder so that argv can be specified more conveniently in
  command line execution.
* Increase information included in warning of mount failure

Add command line help and assert uidmap helpers

* Assert newuidmap helper programs exist before forking for easier debug
* Add config VARDOCS, argparse helpstrings, and --dump-config command line
  options

Improve some configuration options, shuffle files around, add some docs