Add Validation + Synchronization on Likemark Creation and Import (Every Http Post)

[Tower450]

• Post and Import: Verify if id is not already saved in the database before creation.

• FrontEnd: Synchronize position in the likemark hiearchy for a post.

(Fun part and very important)

• Import: Implement synchronization with a changed/new netscape file. Which means if you import x number of time into the database the same or different version, it should not have copy of the ulterior version of the netscape file, but only those represented from the last imported netscape file.

EDIT FOR IMPORT : all likemarks should be duplicated x times with the same hierarchy from the root with all different uuid.

(Fun part and very important)

• Import: Do the same synchronization + keeping the one that were not coming from the netscape file (Added by the API post call).