Added more update-options
Revised try/catch blocks

Changed add-,cancel-, and clear function
Revised class-structure

fixed iOS 8.1 build fails with linker error #365

There was a copy paste error in the plugin.xml. That's why 2 files were not compiled.

Added:
Ability to schedule, clear and cancel multiple notifications at once
Ability to update existing notifications
Clear methods on JavaScript-side

Edit README to fix grammar and standardize English

Added clear and clearAll functions and onClear callback for android on Java-side and fixed Problem with manually cleared notifications on android.