(TWILL-100) Updates to Examples and Documentation

This includes changes to the examples and documentation to aid new users in getting started with the example applications.  Below is a summary of included changes:

twill-examples-yarn
* POM: removed "provided" scope, which prevented dependencies from being packaged in the jar
* BundledJarExample: was incorrectly parsing the command line arguments.  BundleJarRunner.Arguments expects 1) Jar File, 2) Lib Folder, 3) Main Class Name, 4) Arguments.  Previously it was omitting the Lib Folder causing failures when attempting to run the example.

twill-examples-echo
* POM: added slf4j-simple dependency to allow logging

GettingStarted.md: added a new section to the end providing instructions on how to run the example applications.

Finally, I added an Eclipse section to the .gitignore