Add a method for generating the tabkeys for sysdb.

[x4base]

The design of database has been changed in commit 4fa966b.
This method helps update the database by altering the db and generating
the tabkeys from m0,m1,m2,m3,m4 in the old schema.

I don't know whether there is any existing function here. I just can't find one. I am using the Boshiamy Chinese input method. After I upgraded from Fedora 18 to Fedora 20, ibus-table keeps crashing because of this exception: 'tabsqlitedb.py:781:select_words:sqlite3.OperationalError: no such column: tabkeys'. Therefore I wrote this function.

But I don't really know in which function should this method be called. I tried to call it in tabsqlitedb.init(), but you need the root permission to modify the sysdb file. Another way is to wrap it into a command line tool to allow the user upgrade the db by himself/herself, but I don't know where to put it either. So maybe please accept this pull request and help me finish it, or tell me what can I do. Thanks!

[x4base]

It can be downloaded from http://boshiamy.com/member_download.php#tab4 . I don't know if you can read Chinese. It's in the 4th tab (with 'IBus' in its name). However, it's for paid member only.
It is in the proprietary license. It mentioned something like 'Copyright by Liu company', 'You cannot convert and re-distribute it'. I think they might release the new version only when they are asked to. Maybe they just haven't known there is a new db schema yet.

I tried to implement the basic part of ibus-table-updatedb. Please review it. Thanks!

[x4base]

mike-fabian > Or maybe an option to /usr/bin/ibus-table-createdb to reconstruct the source from the .db file again.

Is it really better? I'm not sure in what situation it would be useful. After you reconstructed the source, you still have to generate the db, right? Isn't just updating more straightforward? Or do you mean you think it is useful to have both features? Maybe having both src-to-db and db-to-src conversions would make the code harder to maintain?