Content conflicts on non-string values are not handled properly

[slarse]

As of #42 nodes can have both primary and secondary values. Currently, if there is an unresolved conflict in the secondary values, the primary value is flagged as conflicting in the output. For example, the followng merge scenario has an obvious conflict in the visibility modifier:

// base
int x = 2;

// left
private int x = 2;

// right
public int x = 2;

But it will actually be flagged like so:

int
<<<<<<< LEFT
x
=======
x
>>>>>>> RIGHT
= 2;

Which obviously is horrendously incorrect. This needs to be resolved, but it would probably be best to identify some more secondary values first to make sure it's resolved in a generalized fashion.

[slarse]

Secondary values isn't a thing anymore as of #60, but there are still issues with pretty printing conflicts on non-string content values.