added ability to view a list of all projects

mistakenly removed link_to  "New Project" from index.html.erb because it
didn't appear in the text!
Added updating projects functionality

key concepts to remember
link_to  in 'show' view to get to 'edit' page
render "form" to display partial rather than rewriting it
render action-method to redisplay edit page
Implemented destroy (delete) functionality
Project doesn't exist

Users should be redirected back to the projects page if they try to
access a project that doesn't exist.
Implemented creating tickets for a project

Included has_many :tickets in projects.rb model to establish db
relationship between projects and tickets.  When generating tickets
model indicate :project is a reference to create foreign key.