This is old addon of mine, I wanted to release when new blender booleans will be added to master, but it seems it will take a while, so here it is.
Located in left Tool Shelf-> Tools-> Trim View.
- knife trim - cut geometry with knife tool
- trim by selection - cut mesh in plane based on selected geometry normal. To define plane - select 2 or more vertices. Then you can offset the cut plane by pressing F6 and changing depth parameter.
The pie menu is my private setup, and addon is not distributed with it.
Grab it from here (free for now, but maybe I will sell it for 1$ in future, because usually nobody donates)