Create shared bibtex database
Make several small changes to the overall document

* Add a section for references
* Tweak the title and author to something slightly more descriptive
* Remove numbering for parts
* Add some minor motivation for the document
* Add URL for FSF to licensing information.
Add content to shared LaTeX files

* Add macros to common preabmle
* Change some of the package parameters in the common preamble
Add additional cointegration notes to text

These are a few hand-edited notes on the cointegration material from
my lectures.  There are errors.
Add to VAR material from lecture prep

Mostly Bayesian stuff:
* Conjugate priors and estimation for VAR modesl
* partial identification in SVARs
Bump version