components: preserve them over import and export.

UFO component handling.

This is aimed at part 1 of the comment in issue 298:
https://github.com/metapolator/metapolator/issues/298#issuecomment-63084752
    "roundtrip: make sure that components from imports end up in the skeleton layer. Make sure that components from the skeleton layer end up in the exported UFO. No need to detect circular dependencies here."

Specifically I have tested with the following and the chain of component references is preserved in mpout.ufo from 
the components.ufo sample file.

    $ alias mp=./metapolator
    $ rm -rf /tmp/mptest; mp init /tmp/mptest
    $ mp import ./data/fonts/test/components.ufo  /tmp/mptest/components2
    $ mp export /tmp/mptest/components2 /tmp/mpout.ufo


Yeah, one piece of information is missing! Good that you are asking!
We should rename `transformation` above, otherwise it collides with our new cps-parameter name.
```
 _p._cps_whitelist = {
    baseGlyphName: '_baseGlyphName'
  , originalTransformation: '_transformation'
}
```
Then, when we start to read the transformation matrix of the compontent from CPS (using the StyleDict of the component, that is returned by `getComputedStyle` of Controller) we need to define the default value of the  transformation in the `centreline-skeleton-to-symmetric-outline.cps` file i.e. in https://github.com/metapolator/metapolator/blob/master/app/lib/project/parameters/outputConverter.js
```
component {
    transformation: originalTransformation
}
```

From within CPS rules can change that definition of `transformation`, e.g.:
```
glyph#b component:i(0){
    transformation: (Translation 100 100) * originalTransformation
}
```