Added alarm pulsing option to PVWidgetEditpart.

Current implementation defaults to false, and if option is selected will
pulse any alarm sensitive part of the widget every 1.5s for major,
and every 3s for minor
Hide Pulsing Alarm field if we have a native action button in the same way as we hide background color alarm sensitive
Don't constantly recalculate the border when in alarm pulsing mode as it will never change
Added eclipse preferences to allow MINOR and MAJOR pulsing alarm periods to be set by user.
Get the framerate for the screen update from OPI_GUI_REFRESH_CYCLE
Merge pull request #653 from dls-controls/pulsing-alarm

Added alarm pulsing option to PVWidgetEditpart.