Shift remove indexes in the schema.

The add index was shifted to be able to or it with the property attributes. However, the remove wasn't because it didn't work with attributes. This could cause conflicts because of the different format from the add indexes.
Emit leave instead of break in try/catch.
Cleaned up the JintEngine class.
Removed the Options enum and implemented strict correctly.

The Options enum was used whether the engine should run in strict mode and/or EcmaScript5 mode. The enum has been removed. EcmaScript5 is now the default and strict is implemented correctly, using the 'use strict'; constuct.

Bug: #46