panel scroll locking when side menu is open

Issue
-
See issue #468, main panel is scrollable when side menu is open, also when slidemenu plugin is used,scrolling is possible while sliding menu.

Test Case
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- Open kitchen sink app and toggle side menu, notice that main panel is scrollable.
- Swipe main panel to right and also move up/down, notice that main panel is scrollable


Fix
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- implemented main panel scroll lock/unlock when side menu is open/closed.
- used `$().scroller().lock()` and `$().scroller().unlock()` functions of scroller plugin when side menu is shown or hidden.
- added an option param for `$.ui.toggleSideMenu()` to disable scroll locking, by default if no option is specified then - panel scrolling is locked when side menu is open.
- this will first check if `af().scroller` plugin exists.