webadmin,userportal: Control verbosity of GWT compiler

Using INFO as default GWT compiler log level.

Can be customized through "gwt.logLevel" property,
for example:

  make DEV_EXTRA_BUILD_FLAGS="-Dgwt.logLevel=TRACE" ...
  make EXTRA_BUILD_FLAGS="-Dgwt.logLevel=TRACE" ...

Change-Id: I4d7333078bf4718687004938fa55a082bbcd6426
Signed-off-by: Vojtech Szocs <vszocs@redhat.com>