WL-3326 : Hook up Lessons to Mneme (vs Samigo)

4 main changes here:
Enable the “optional” profile in tool/pom.xml
Remove the bits about Assignments 2 and Yaft in opt-applicationContext.xml
Set right version numbers and dependency type in main pom.xml
Change context.xmls to use MnemeEntity rather than SamigoEntity
WL-3326 : typo
WL-3326 : Remove dependency on rutgers repo
WL-3326 : Remove yaft/assignment2 dependencies (and code)
WL-3326 : Remove yaft and assigments2 versions/scopes
Merge pull request #1 from ox-it/WL-3326

WL-3326 : Hook up Lessons to Mneme (rather than Samigo)