JS: pull all ui-initialization calls into GUIFrame

Signed-off-by: Harvey Harrison <harvey.harrison@ausenco.com>
JS: hide eventManager getter inside Entity until we decide if this should be exposed

Signed-off-by: Harvey Harrison <harvey.harrison@ausenco.com>
JS: move static initialization out of Simulation constructor

Now that multiple Simulations can be defined, avoid reinitializing static state
each time.

Signed-off-by: Harvey Harrison <harvey.harrison@ausenco.com>
JS: ensure startDate, startTimeInput are properly reset on clear()

Signed-off-by: Harvey Harrison <harvey.harrison@ausenco.com>
JS: test for null processes when clearing the event stacks

Scheduled Events do not have an allocated process anymore and do not need to be
killed in basicInit.

Signed-off-by: Harvey Harrison <harvey.harrison@ausenco.com>