Deprecate various WebView related methods

WebSettings:
PluginState - plugins depreacted and will not be supported in future.
setRenderPriotity - b/6335436
setLightTouchEnabled - b/7683972 it's s no-op.
setAppCacheMaxSize - has a sensible default and will  be obsolete in
                     future with HTML Quota Management API. b/6236763

WebStorage.setQuotaForOrigin - same as setAppCacheMaxSize

WebView:
clearView, showFindDialog - buggy, can be achieved otherways
savePassword - not useful/usable in practice; see b/5012826
             - stock browser used hidden APIs to achieve this feature

WebIconDatabase:
Other than the open() method, this does nothing useful. b/7331507

Change-Id: I01793f7b34978046eb54033477fca2da96e69c2e