Restructure source files

~~This pull request is based on previous work (#12, #16, #17).  Those should be merged, in that order, before this is merged.  This is why you see a lot more commits here than there should be.  They will clear out when the other work is merged.  The commits of interest in this pull request are 1477784 and every commit following it.~~

This pull request does a few things:

1. Removes the `uq` prefix from all filenames;
2. Changes the header install location from `$prefix/include` to `$prefix/include/queso`;
3. Does 1. and 2. in such a way that out-of-source builds still work.

Item 1 is mostly hygiene, the prefix was extraneous.  Further filename changes may be suggested here.  I'm open.  Item 2 is an enhancement; tidying up installed files so that queso's installed files (now without an identifying `uq` prefix) so that they reside in a compartmentalised `queso` directory.  Any user code will change in the following manner:

**Before**:
```c++
#include <uqEnvironment.h>

int main(int argc, char ** argv) {
  return 0;
}
```

**After**:
```c++
#include <queso/Environment.h>  // <-- Note change here

int main(int argc, char ** argv) {
  return 0;
}
```

`make`, `make check` and `make distcheck` all succeed.