Added priority feature

I've adde a priority feature so you can type c+tab h+tab l+tab for critical high low priority. I've choosed this priority because "critical" has more chars than "high" and "high" has more chars than "low" so you have the evidence of a bigger color label for high priority task.

I've also modified al themes to have the coloring in all cases
Now there is plus in the beginning of line.
Don’t worry I’ll merge by hand today.
Thank you for pull request.

Btw, GitHub doesn’t notify about new commit so in general you have to comment to let ppl know about changes.
When I did my first pr all `\n` were changed to `\r\n` :smile: