Added new AngelList plugin; improved INI support

Lookups now also include data from the AngelList API by default.  You
can exclude the data with "-ea=1" if you want.

The config INI file now supports specifying input and output files
directly.  See the example INI for how to set them.  Note:  values set
on the command line will override the file settings.  The keys code
path has been updated to reflect that as well.

Updated to the latest scooper_common files, including a new common
config class for reading Scooper INI files.

As part of adding AngelList support, generalized some functions and
moved them to the base plugin class.  This will hopefully speed up
adding future ones a bit more.  Some of the plugin specific function
names have been changed to use the base classes naming convention as
well.