added basic vector clock utility.

Ignore-this: 9ec48290cd48431b5dd789a04844af5d

The idea is to expose vector clocks to apps so that they can easy implement
eventual consistency and be able to partially order events.

darcs-hash:20140920052129-c21fe-16db8db99a4aa9c4c50f275057d57df91a681ed9
added vector clock in app editor

Ignore-this: 8fb8b7f0d6f4531c502a9d69122520d2

A vector clock is now used to throw out messages that are older.

darcs-hash:20140920055510-c21fe-de39259eaa95018190f06376f70153df48a2d75d
now data is updated when you remove a key

Ignore-this: 9a58daccb06efeee7d69aac3e4a023fb

darcs-hash:20140920055657-c21fe-12a6d68e4a19855a72e7ad8877e4fcfcd0eed102
added a clear function to disk_store which deletes everything

Ignore-this: cf2fd3aed456caf8fad8a0f63f8c3478

darcs-hash:20140920055753-c21fe-37bd9cc5a5c94864cfe83e16664c3efca69e37df
added clear in app editor for data to fix bug when deleting key

Ignore-this: 18bec8c474f7cebf044dcc95dffa1cc9

darcs-hash:20140920055822-c21fe-92eec4a781964791b1cec2ebb6c41b2f2700fa8d
fixed bug where exception was thrown for each script message

Ignore-this: 171a4aadf47e454e597a86d319be2ace

darcs-hash:20140920055844-c21fe-149d5dd8d59d79190fb771f30baffaf1fe0078f7