Make wire-cell-data a 'data only' package.

[brettviren]

Currently, wire-cell-data is packaged like a normal package that transforms source to architecture and compiler specific binary. But, in fact only version matters. This leads to duplication of data and wasted storage when a Spack install area spans more than one compiler and/or architecture. Ideally we could install it as a "NULL" or "wildcard" arch/comp. So far, it looks like Spack does not support this and this issue is a bookmark to watch for development. One place it is discussed:

spack/spack#7550