Add Initial Search Task Model, Controller & Views
Search Task searches view.

Copied Monthly Search Step 1 to Search Tasks searches view.
Added CSS layout Search Tasks searches view.
Minor edits to Search Tasks index view.
Search Task publications & metadata views.

Copied Monthly Search Steps 2/3 to Search Tasks publications/metadata views.
Add Complete button to Search Tasks navigation.

Complete button should validate searches, publications, and metadata
associated with the Search Task and then close or complete the task.
Views and routes updated, controller action still a stub.
Fix Publication model method 'create_for_pmid'

Was not passing search_task parameter to 'new_for_pmid'.
Fix #10, Fix #14.  Search engine/term dropdowns.

Change search engine/term dropdowns to comboboxes (done previously).
Add 'last search engine/term' fields to Search Tasks.  Retain values
whenever a new search record is created.
Major update to monthly search.

Added Search Tasks model to organize monthly searches.
Removed 'monthy literature search' steps and replaced with a display
organized around Search Months.
Updated 'pre-search' to work correctly.