Review and add more compiler options of GWT 2.8.0+

[jiakuan]

Need to review the latest "GWT Compiler Options" section on this page:
http://www.gwtproject.org/doc/latest/DevGuideCompilingAndDebugging.html

[jiakuan]

Looks like only two compiler options of GWT 2.9.0 are missing:

  -[no]checkAssertions                              Include assert statements in compiled output. (defaults to OFF)
  -setProperty                                      Set the values of a property in the form of propertyName=value1[,value2...].

Anyone wants to take the "challenge" to add them? :)

[chwalker-fadv]

ok, so i picked up the "-setProperty" parameter (as i needed it) for this in #78