Polish translation file

Added file with the Polish translation (timemanager_pl.ts)
Merge pull request #73 from gelaner/master

Polish translation file
Merge pull request #76 from carolinux/support_integer_timestamps

Add support for integer timestamps, tests, partially abstract datetime h...
added Date column to tweets.dbf
Update README.md
should fix #64 Export Video error: no attribute 'animationFrameCounter'

tested on Ubuntu
Merged master. Tweets.dbf has t,t_slash, forever, t1965, t1765, t1165 but no date(20111112) column after merge, can add it later