This adds support for literal strings in functions.

The main use case for this is to support the
to_tsvector function so you can create full
text indexes on a given column. This is probably
pushing the limit of regex parsing here, since
more complicated expressions are going to quickly
result in an unmaintainable regex.
Handle types of expression parameters
Get the schema dumper working.
Merge branch 'support-literal-strings-in-functions' of git://github.com/reinteractive-open/pg_power into reinteractive-open-support-literal-strings-in-functions
Merge branch 'reinteractive-open-support-literal-strings-in-functions' from github.com/reinteractive-open

* reinteractive-open-support-literal-strings-in-functions:
  Get the schema dumper working.
  Handle types of expression parameters
  This adds support for literal strings in functions.

Task 9929