Tidy up UQ ADF

It looks like there is quite a bit of redundancy in the functions offered for UQ. In particular, I don't think the UQMeasurementset is currently very useful. Either we should extend it and offer it for all algorithms, or get rid of it and always use separate vectors of parameters/positions and solutions (or a std::pair thereof).

However, since I am not the one currently using this algorithm (and don't know what all the new functions do) I don't want to change it more than I already did. @trunschk can you have a look at it?

Update:

• replace UQMeasurementset by the two vectors of rank-1 measurements and their corresponding values
• add convenience functions that evaluate a given basis at given points and return the two vectors of rank-1 measurements and values
• remove the dimensions argument from uq_ra_adf
• define uq_ra_adf_iv as overloaded version of uq_ra_adf
• clean up the interface for uq_ra_adf