Remove preferences cache, except for the built regex object

[evandrocoan]

As suggested on wbond/package_control_channel#8629 (comment), after Sublime Text core fixes the issue sublimehq/sublime_text#2548, it will be safe to access the Sublime Text settings directly and the local settings cache will (Pref object) will not be required, except for the regex object cache (as regexes objects are pretty expensive to be built).

[eugenesvk]

Seems like that issue you referenced was fixed in build 4170, so can use the native cache (and add a min version requirement?)?