Bitcoin-Qt: updates to addressbookpage

- use labelExplanation for sending and receiving tab and move the string
  from the ui-file to the source
- ensure that the table holding the label and address is resized so that
  the address column fits the address and the label column is stretched to
  fit the window size
- rename some stuff for much easier readbility in the code (I find it hard
  to get the meaning of stuff like labels or buttons)
remove proprietary psd file mentioning from assets-sttribution.txt

Signed-off-by: Jonas Schnelli <jonas.schnelli@include7.ch>
Merge pull request #2465 from jonasschnelli/master

update assets-sttribution.txt (-psd file +svg file)
Merge pull request #2443 from Diapolo/Qt_addrbook

Bitcoin-Qt: updates to addressbookpage
small indentation, space, formatting fixes (no code changes)
Merge pull request #2456 from Diapolo/code-layout

small indentation, space, formatting fixes (no code changes)
Merge remote-tracking branch 'source/master'