Added synchronized flushing with Magento's cache & all required changes henceforth

[hvanmegen]

Added synchronized flushing with Magento's cache because I felt like I was adding an additional step in my customers workflow that was completely unnecessary.

• Added observers to listen for adminhtml_cache_flush_system and adminhtml_cache_flush_all events and perform a flushAll accordingly.
• Added Dutch translations
• Added adminhtml interface configuration to set up synchronized flushing
• Added extra help comment (and translations).
• Updated the modman file
• Changed the README.md file to reflect the changes

I had to move some functionality from the controller to the helper in order to call it easily from my Observer.php.

The synchronized flushing is disabled by default, so existing installations should have no issues.

I could not translate the newly added translatable strings to Korean, but I left the english ones in there.

[steverobbins]

@hvanmegen Thanks for your contribution and clean code!

[hvanmegen]

I guess I must have been psychic about the 1.4.5 release.. I added another pull request for a minor patching of the observer naming; it was copied from another project of mine and I accidentally forgot that it was in there. Since my 'mageboost' module was installed, the observers worked as expected, until I went wondering why I couldn't flush my Full Page Cache anymore :)

I re-checked all other files; no other incorrect references were found.. this should be the only minor bug to this update.

My apologies for having this slip by me; I'll test my modules on clean platforms from now on. #SmarterEveryDay