Activity info

This pull request intend to improve our overview of selected activity. I added new attributes to Activity (key, cmdline, exe). Key is compound of name and title and serves to identification of activity. It should resolve issue #5 .

Regarding GUI: I'm not big fan of what I chose to implement. The Textview at side of Category tabs has some flaws:
* The words like Name, Title are not distinct (I would prefer it in bold case but I know about no easy way how to do it)
* If you try to display info about some java application (PyCharm in my case) you will see in cmdline field very long string, because every java program is started with like thousand flags.

Do you have any suggestions how to change it? 

Also what do you think about adressing out activities with name + title? We will have a lot activities this way, because of web browser has different title for every website. On the other hand we cannot use just name itself because for Waktu it would be just: "python2.7", for java application just "java".

Please test it and tell me every suggestion and critique you can think of.