Incremental, old progress.
First pass at adding VASP support (doesn't actually deal with VASP).

The big issue is that VASP and QE use very different output files.
One approach would be to turn each output file into a universal
data structure, that could then be read.  I think this solution
is too heavy for now.

Instead, the patterns which are used to pick out the output values
are put in a dict with keys corresponding to output formats.  In
each run directory, a loop looks for types of output files and
uses the appropriate sets of patterns.

This commit makes the above generalization and works for total
energy and pressure in qe runs.

In the future, this pattern <=> output file association could be
generalized to a function <=> output file generalization, which
might be necessary for reading some more complicated things.
Added display outputs, which are printed without comparisons.
Computed test_output and display_output by generalizing intrinsic.

disp_output now takes a typ argument (default: 'display') that
specifies how to map the values to outputs.  Four options are
 * 'intrinsic': takes diff (val - ref)
 * 'extrinsic': takes rel error (val - ref) / ref
 * 'ratio': (val / ref)
 * 'display': just (val)
Bugfix in def of 'ratio' (inverse) and added outputs
Debugging and touch up.

Executable copies only happen if needed, changed some names,
put in some divide by zero checks...  Nothing big.
Added VASP analogs of some QE strings.
Commented out numpy deps.