Molecular moments and some other minor things

A summary of the changes in this pull request to date:

* added parsing code for `moments` to all parsers except Gaussian and Jaguar
    * parses the last encounterd moment, in line with other property attributes such as `atomcharges`
    * use Debye, Buckingham and similar units with higher powers for angstrom
    * convertor utility updated accordingly
    * add checks for dipole moment and higher moments in SP unit test, and some regressions
    * still need to add the reference point as the first element in `moments` for all parsers
* added a `--verbose` option to ccget
* sorted list of attributes (also the ones printed by ccget)